docs(spec): describe git worktree sandbox path via temp dir placeholder

The GitWorktreeSandbox implementation (PR #5998) creates worktrees in the
system temp directory using tempfile.mkdtemp() with the prefix
ca-sandbox-<plan_id>-, producing OS-specific paths (e.g.,
&lt;SYSTEM_TEMP_DIR&gt;/ca-sandbox-<PLAN_ULID>-XXXXXX/).

The spec previously showed the worktree path as a .worktrees/ subdirectory
inside the repository (e.g., /repos/api/.worktrees/plan-01HXM8). This was
incorrect and inconsistent with the implementation.

Changes:
- Update all plan execute output examples (Rich/Plain/JSON/YAML) to use the
  <SYSTEM_TEMP_DIR> prefix placeholder instead of hard-coding /tmp
- Update the end-to-end workflow examples (strategize + execute panels)
- Add explicit documentation of the git worktree path format in the
  Sandbox Implementation Strategies section, including rationale
- Update the changelog to reference the cross-platform placeholder

Triggered by: merged PR #5998 (GitWorktreeSandbox implementation)
ISSUES CLOSED: #6343

CHANGELOG.md

@@ -48,6 +48,9 @@ The format follows [Keep a Changelog](https://keepachangelog.com/en/1.1.0/).
 
 ### Changed
 
+- **Specification** (#6343): Documented that git worktree sandboxes are created in
+  the system temporary directory (rendered as `<SYSTEM_TEMP_DIR>/ca-sandbox-<PLAN_ULID>-XXXXXX/`)
+  so example `plan execute` outputs stay platform-accurate instead of hard-coding `/tmp`.
 - **Automation Tracking Format**: All automation tracking issues now use a standardized
   header format with mandatory `Reporting Interval: <interval> (Next report expected: <ts>)`
   declarations, enabling precise staleness detection.

docs/reference/cleanup.md

@@ -129,9 +129,11 @@ Cleanup Scan Results (dry-run)
   Backups          scanned=5  to remove=2  skipped=0
 
 Stale items found:
-  [sandbox] /tmp/ca-sandbox-plan123-abcd (3 days old)
+  [sandbox] <SYSTEM_TEMP_DIR>/ca-sandbox-plan123-abcd (3 days old)
   [checkpoint] .cleveragents/checkpoints/plan456/checkpoint_003.json (excess)
   ...
+
+> ℹ️ Replace `<SYSTEM_TEMP_DIR>` with the temp directory for your OS. On Linux this is typically `/tmp`, on macOS it is the value returned by `getconf DARWIN_USER_TEMP_DIR`, and on Windows it resolves to `%LOCALAPPDATA%\Temp`.
 ```
 
 Purge only sandboxes and checkpoints (default):

docs/specification.md

@@ -12947,12 +12947,12 @@ Start or resume execution for a plan.
     │ <span style="color: #5599ff; font-weight: 600;">Attempt:</span> 1                       │
     ╰──────────────────────────────────╯
 
-    ╭─ Sandbox ──────────────────────────────────╮
-    │ <span style="color: #5599ff; font-weight: 600;">Strategy:</span> git_worktree                     │
-    │ <span style="color: #5599ff; font-weight: 600;">Path:</span> /repos/api/.worktrees/plan-01HXM8    │
-    │ <span style="color: #5599ff; font-weight: 600;">Branch:</span> cleveragents/plan-01HXM8C2         │
-    │ <span style="color: #66cc66; font-weight: 600;">Status:</span> active                             │
-    ╰────────────────────────────────────────────╯
+    ╭─ Sandbox ──────────────────────────────────────────────────────────╮
+    │ <span style="color: #5599ff; font-weight: 600;">Strategy:</span> git_worktree                                             │
+    │ <span style="color: #5599ff; font-weight: 600;">Path:</span> &lt;SYSTEM_TEMP_DIR&gt;/ca-sandbox-01HXM8C2ZK4Q7C2B3F2R4VYV6J-XXXXXX │
+    │ <span style="color: #5599ff; font-weight: 600;">Branch:</span> cleveragents/plan-01HXM8C2                                 │
+    │ <span style="color: #66cc66; font-weight: 600;">Status:</span> active                                                     │
+    ╰────────────────────────────────────────────────────────────────────╯
 
     ╭─ Strategy Summary ─────────────────────╮
     │ <span style="color: #5599ff; font-weight: 600;">Decisions:</span> 8                           │
@@ -12987,7 +12987,7 @@ Start or resume execution for a plan.
 
     Sandbox
       Strategy: git_worktree
-      Path: /repos/api/.worktrees/plan-01HXM8
+      Path: <SYSTEM_TEMP_DIR>/ca-sandbox-01HXM8C2ZK4Q7C2B3F2R4VYV6J-XXXXXX
       Branch: cleveragents/plan-01HXM8C2
       Status: active
 
@@ -13019,7 +13019,7 @@ Start or resume execution for a plan.
         "phase": "execute",
         "sandbox": {
           "strategy": "git_worktree",
-          "path": "/repos/api/.worktrees/plan-01HXM8",
+          "path": "<SYSTEM_TEMP_DIR>/ca-sandbox-01HXM8C2ZK4Q7C2B3F2R4VYV6J-XXXXXX",
           "branch": "cleveragents/plan-01HXM8C2",
           "status": "active"
         },
@@ -13056,7 +13056,7 @@ Start or resume execution for a plan.
       phase: execute
       sandbox:
         strategy: git_worktree
-        path: "/repos/api/.worktrees/plan-01HXM8"
+        path: "<SYSTEM_TEMP_DIR>/ca-sandbox-01HXM8C2ZK4Q7C2B3F2R4VYV6J-XXXXXX"
         branch: "cleveragents/plan-01HXM8C2"
         status: active
       worker: "local/executor"
@@ -19272,6 +19272,24 @@ Different resource types require different sandbox strategies:
 Pros: natural rollback, diff support, efficient
 Cons: requires git
 
+**Git worktree path format**: The worktree is created in the **system temp directory** (whatever `tempfile.gettempdir()` returns on the host OS) using `tempfile.mkdtemp()` with the prefix `ca-sandbox-<plan_id>-`. This produces paths of the form `<SYSTEM_TEMP_DIR>/ca-sandbox-<PLAN_ULID>-<RANDOM>/`. The worktree is **not** created inside the repository directory (e.g., not in `.worktrees/`). This avoids polluting the repository, leverages OS-managed cleanup on reboot, and guarantees path uniqueness. The branch name follows the pattern `cleveragents/plan-<PLAN_ULID_PREFIX>`.
+
+Example paths:
+- Linux: `/tmp/ca-sandbox-01HXM8C2ZK4Q7C2B3F2R4VYV6J-a3f7b2/`
+- macOS: `/var/folders/<hash>/T/ca-sandbox-01HXM8C2ZK4Q7C2B3F2R4VYV6J-a3f7b2/`
+- Windows: `%TEMP%\\ca-sandbox-01HXM8C2ZK4Q7C2B3F2R4VYV6J-a3f7b2`
+
+!!! tip "Finding `<SYSTEM_TEMP_DIR>`"
+    The value depends on the host operating system:
+
+    - **Linux**: `echo "$TMPDIR"` if set, otherwise `/tmp`
+    - **macOS**: `getconf DARWIN_USER_TEMP_DIR` resolves to `/var/folders/<hash>/T/`
+    - **Windows**: `%LOCALAPPDATA%\\Temp` (also accessible via `echo %TEMP%`)
+
+    CleverAgents reads whatever `tempfile.gettempdir()` returns, so custom
+    deployments that override the process temp directory will automatically
+    inherit that location.
+
 **2. Filesystem copy sandbox**
 
 * Copy project directory to a sandbox directory
@@ -36645,12 +36663,12 @@ Because the automation profile is `manual`, the plan stops and waits after creat
 │ <span style="color: #5599ff; font-weight: 600;">Attempt:</span> 1                              │
 ╰─────────────────────────────────────────╯
 
-╭─ Sandbox ───────────────────────────────────────────────────────╮
-│ <span style="color: #5599ff; font-weight: 600;">Strategy:</span> git_worktree                                          │
-│ <span style="color: #5599ff; font-weight: 600;">Path:</span> /home/dev/projects/api-service/.worktrees/plan-01HXR1C1   │
-│ <span style="color: #5599ff; font-weight: 600;">Branch:</span> cleveragents/plan-01HXR1C1D2                            │
-│ <span style="color: #66cc66; font-weight: 600;">Status:</span> active                                                  │
-╰─────────────────────────────────────────────────────────────────╯
+╭─ Sandbox ──────────────────────────────────────────────────────────────────╮
+│ <span style="color: #5599ff; font-weight: 600;">Strategy:</span> git_worktree                                                     │
+│ <span style="color: #5599ff; font-weight: 600;">Path:</span> &lt;SYSTEM_TEMP_DIR&gt;/ca-sandbox-01HXR1C1D2E3F4G5H6I7J8K9L0-XXXXXX      │
+│ <span style="color: #5599ff; font-weight: 600;">Branch:</span> cleveragents/plan-01HXR1C1D2                                       │
+│ <span style="color: #66cc66; font-weight: 600;">Status:</span> active                                                             │
+╰────────────────────────────────────────────────────────────────────────────╯
 
 ╭─ Strategy Summary ────────────────╮
 │ <span style="color: #5599ff; font-weight: 600;">Decisions:</span> 4                      │
@@ -36758,12 +36776,12 @@ The strategy actor has read the codebase, identified the relevant files, and pro
 │ <span style="color: #5599ff; font-weight: 600;">Attempt:</span> 1                              │
 ╰─────────────────────────────────────────╯
 
-╭─ Sandbox ───────────────────────────────────────────────────────╮
-│ <span style="color: #5599ff; font-weight: 600;">Strategy:</span> git_worktree                                          │
-│ <span style="color: #5599ff; font-weight: 600;">Path:</span> /home/dev/projects/api-service/.worktrees/plan-01HXR1C1   │
-│ <span style="color: #5599ff; font-weight: 600;">Branch:</span> cleveragents/plan-01HXR1C1D2                            │
-│ <span style="color: #66cc66; font-weight: 600;">Status:</span> active                                                  │
-╰─────────────────────────────────────────────────────────────────╯
+╭─ Sandbox ──────────────────────────────────────────────────────────────────╮
+│ <span style="color: #5599ff; font-weight: 600;">Strategy:</span> git_worktree                                                     │
+│ <span style="color: #5599ff; font-weight: 600;">Path:</span> &lt;SYSTEM_TEMP_DIR&gt;/ca-sandbox-01HXR1C1D2E3F4G5H6I7J8K9L0-XXXXXX      │
+│ <span style="color: #5599ff; font-weight: 600;">Branch:</span> cleveragents/plan-01HXR1C1D2                                       │
+│ <span style="color: #66cc66; font-weight: 600;">Status:</span> active                                                             │
+╰────────────────────────────────────────────────────────────────────────────╯
 
 ╭─ Progress ────────────────────────────────╮
 │ <span style="color: #66cc66; font-weight: 600;">✓</span> Collect context (0.4s)                  │