Implements the spec-required AccessProjection type with fields access_path,
protocol, crosses_sandbox, and read_richness per docs/specification.md lines
25100-25114. Updates ResourceHandler.project_access to accept the spec-required
parameters (binding_resource, target_resource, containment_path, sandbox) and
return AccessProjection | None per spec lines 21691-21698.
Separates access-control logic into a new check_access method returning
AccessCheckResult, resolving the semantic confusion between authorization
(check_access) and routing/reachability (project_access).
Updates all concrete handler implementations and test step definitions to use
the new signatures. Adds TDD Behave scenarios tagged @tdd_issue @tdd_issue_1444
verifying the spec-required fields and method signatures.
ISSUES CLOSED: #1444
Epic-Reference: #398
HAL9000
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