docs(#54): F-4 legacy annotation + F-5 fixture convention -- AUDIT-01 housekeeping

INTEGRATION-AUDIT-01 (#50) §10.4 / §10.5 housekeeping carry-over.

F-4: annotate 14 remaining legacy Phase R'/Q sample-text hits across 10
src/ files with inline marker `# [legacy Phase R'/Q example -- INTEGRATION-AUDIT-01 §10.4]`.
Comment-only. No string-literal / regex / sample dict value mutated.
fit_verifier.py L612 marker keeps Phase Z partial-live import graph
(FitAnalysis / RoleFit / redistribute / salvage) byte-precise.

F-5: docs-only addendum -- §10.5.1 in INTEGRATION-AUDIT-01-REPORT.md +
tests/CLAUDE.md fixture convention note. No root tests/fixtures/ dir
created; existing tests/phase_z2/fixtures/ convention preserved. Documents
test-only sample-reference allowance vs src/** runtime prohibition.

Out of scope: Phase Z source 11 hits (phase_z2_content_extractor /
failure_router / mapper / retry), production behavior change, #19 work.

Verified: pytest -q tests/phase_z2/ = 157 PASS. git diff +210/-0
(35 src/docs lines + 175 new tests/CLAUDE.md). No behavioral delta.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docs/architecture/INTEGRATION-AUDIT-01-REPORT.md

@@ -521,6 +521,17 @@ Five candidates were produced by Axes 1-4. F-3 + F-2 + F-1 are blocking conditio
   - REPORT §8.2 fourth bullet (`tests/fixtures/` not yet established).
 - **priority / gating** : **optional, very low priority**. Filing is only justified when sample inventory grows; the current state is already aligned with the spirit of the rule.
 
+#### 10.5.1 F-5 docs-only resolution addendum (#54 Stage 3 u5, 2026-05-19)
+
+Per issue #54 Stage 2 plan, F-5 is closed as **docs-only**; no root `tests/fixtures/` directory is created in this work. The current fixture inventory does not justify migration, and the existing convention is sufficient. The convention is recorded here so future anti-hardcoding audits can distinguish fixture / test-only paths from production paths without re-discovering the §8 G6 PASS-WITH-NOTE baseline.
+
+- **Existing convention (DO NOT CHANGE)** : `tests/phase_z2/fixtures/` exists as a YAML regression fixture root (loaded by `tests/phase_z2/test_fixtures_loader.py`). Subdirectories present at audit time : `tests/phase_z2/fixtures/build_layout_css/`, `tests/phase_z2/fixtures/retry_gate/`. This is the canonical home for Phase Z regression fixtures.
+- **Root `tests/fixtures/` (ABSENT)** : not created in #54. If a future change requires a non-Phase-Z, non-YAML fixture corpus (for example, multi-file MDX golden inputs that grow beyond what `tests/phase_z2/test_*.py` can hold inline), the migration must be filed as its own Gitea issue with its own scope-lock per §10.5.
+- **Allowed sample references** : `samples/mdx_batch/**` and `samples/mdx/**` may be referenced from `tests/**` (test-only paths) for integration smoke -- e.g. the existing `samples/mdx_batch/02.mdx` references in `tests/phase_z2/test_pz2_vu_integration.py`. These do not violate the §8 anti-hardcoding rule because the spirit of the rule targets production pipeline code, not test runners.
+- **Forbidden sample references** : production pipeline code (`src/**` runtime path) must NOT hardcode sample-specific MDX filenames or content (e.g. `02.mdx`, `03.mdx`, frame-specific labels keyed to a sample). The 20 legacy Phase R'/Q hits annotated under F-4 (#54 Stage 3 u1-u4) are intentional documented examples in docstrings / comments / glossary regex / sample-data dicts, not runtime input pins; they are out of scope for this rule by §10.4 verdict.
+- **AI-isolation contract** : this addendum is text-only. No production behavior change, no runtime sample-path mutation, no new fixture file. Compatible with PZ-1 (AI = 0 on normal path) and [[feedback_ai_isolation_contract]].
+- **Cross-reference** : `tests/CLAUDE.md` fixture convention note (#54 Stage 3 u5) mirrors the test-only / production rule split documented here.
+
 ### 10.6 Follow-up summary
 
 | candidate | source axis | doc-only? | gates #19? | priority |