Files Changed: prove full-provenance behavior end to end

Acceptance Criteria

• The matrix covers agent, child-agent, user, system, and opaque origins across full, partial, and legacy modes.
• The matrix covers workspace, non-Git external, external repository, internal, binary, artifact, directory, Trash, restore, symlink, alias, and unsupported-provider resources.
• The matrix covers success, denied, failed, aborted, partial, conflict, unavailable, opaque, quota, and expiry outcomes.
• The matrix proves unrelated concurrent writes are never attributed to the active root.
• The matrix proves capability, evidence, and protected metadata do not cross browser, transcript, share, export, telemetry, log, or error boundaries.
• The matrix covers task and explicit spawn aggregation, fork separation, child archival/deletion, old sessions, upgrade epochs, mixed binaries, and rollback.
• The matrix validates keyboard operation and both supported themes for the unified surface.
• Default enablement remains blocked until every required matrix case passes.

Testing Decisions

• Reuse existing server, app, extension-host, sharing, and release-rehearsal harnesses where each already owns a boundary.
• Add only end-to-end fixtures that cross otherwise independent harnesses.

Key Decisions

• This is a release gate, not a confidence-only test suite.
• A passing happy path cannot substitute for coverage of provenance failure modes.

Constraints & Invariants

• Test evidence must distinguish legacy behavior from full-provenance behavior.
• The matrix cannot mutate a real external user directory without an isolated fixture.

Prior Art

• Parent Files Changed: full session-lineage mutation ledger #972
• Existing scoped-diff, external-diff, Sidebar, sharing, and release test suites

Deliberation Resolution

• The matrix is a versioned manifest of case IDs. Each row declares fixture, setup, trigger, expected authorization decision, expected receipts and assessments, permitted display-safe fields, prohibited egress fields, cleanup, and required mode.
• A case is covered only when its row runs and produces its declared observable result. The release gate consumes the manifest and emits all_required_passed only when every required case is green; product-denied outcomes are asserted expected results, not failed tests.
• Fixtures use isolated temporary roots, sandboxed external directories, contained symlinks and aliases, disposable Trash fixtures, deterministic cleanup, and post-run containment assertions. No case uses a real user directory.
• Privacy rows assert both permitted status projection and absence of prohibited evidence or metadata for browser, transcript, share, export, telemetry, log, and error boundaries.

Source

Part of #972. Blocked by #1083.