docs: record P6 implementation, contract, and automated acceptance PASS

PROJECT_STATE.md

@@ -7,7 +7,7 @@
 > ThothII per il repository (app + CLI `thothctl`), (3) come usare l'applicazione ThothII di base
 > (sessioni, domande, gate). Il documento userà parole semplici ed esempi; i dettagli tecnici
 > resteranno nei contratti esistenti. Esempio pratico completo: Policlinico San Donato.
- Last updated: 2026-08-13 (P3+P4+P5 manual acceptance).
+ Last updated: 2026-08-13 (P3+P4+P5 manual acceptance; P6 automated PASS).
 > Point a fresh session here ("read PROJECT_STATE.md") before substantial work.
 
 ### P3 effective configuration and `.tht-dwh` — implementation complete, automated PASS, manual PASS (2026-08-13)
@@ -101,6 +101,38 @@
 - **Manual acceptance:** PASS (owner approval 2026-08-13) — walkthrough section P5 in
   `docs/testing/p2-p6-manual-verification.md`.
 
+### P6 commit-addressed Evidence materialization — implementation complete, automated PASS, manual PENDING (2026-08-13)
+
+- **Scope:** P6 (PRD D6): filesystem Evidence `<id>/evidence` is materialized from the exact pinned
+  Git commit into the immutable revision content root `<registry>/snapshots/<commit>/<id>/evidence`
+  at activation, with a sibling bounded manifest `<id>/evidence.manifest.json` whose digest is chained
+  into `snapshot.json`.
+- **Safety:** fixed Git plumbing (`ls-tree -r -z` + `cat-file blob`), no shell, no mobile checkout;
+  symlinks/gitlinks at any depth, traversal/absolute/duplicate/cross-namespace paths, and non-regular
+  modes are refused. Installation-local bounds (defaults): 4096 entries, 64 MiB total, 8 MiB per
+  file, 4096 path bytes, 1 MiB manifest; a size-sum preflight runs before writing and no partial root
+  is published. Re-activation reuses a valid root and fails closed on a tampered manifest.
+- **Engine:** `evidencePolicy` no longer stops filesystem sources (`evidence_materialization_required`
+  retired); `preprocess evidence`/`preprocess run` operate on the materialized root. Evidence Qdrant
+  records remain revision-scoped; corpus ACTIVE is revision-qualified. HTTP/S3 Evidence is unchanged.
+- **Retention:** materialized roots live inside the commit-addressed snapshot directory, so they are
+  retained while pinned and removed by the existing snapshot retention scan when unreferenced.
+- **Key files:** `backend/src/workspaces/evidence-materialization.ts` (+test),
+  `backend/src/workspaces/git-repository.ts` (`evidenceTreeObjects`/`evidenceTreeId`/
+  `evidenceBlobBytes`/`gitObjectSize`), `backend/src/workspaces/registry.ts` (activation staging +
+  integrity chain), `backend/src/workspaces/preprocessing-service.ts` (stop removal),
+  `backend/src/workspaces/types.ts` + `config.ts` (limits), `docs/contracts/
+  workspace-preprocessing-cli.md`.
+- **Gates:** backend **698/698** + tsc clean; Go build+test 9/9 (unchanged); harness focused suites
+  pass. Full-suite re-run and the clean-state process goal recorded at the acceptance gate.
+- **Automated acceptance:** PASS 10/10 (run `p6-7a4c4d0ebb63399cfa9f674738b9e8fc`, report
+  `.artifacts/p6-integration/p6-7a4c4d0ebb63399cfa9f674738b9e8fc/` retained via `--keep`, bound to
+  clean source commit `124891bbfe8dc8270e8b58c4206150eb8bebeaa7`): preflight, clean_state, ownership,
+  activation_materialization, evidence_preprocess, revision_isolation, unsafe_tree_refused,
+  bound_refused, secret_scan, cleanup_confinement. Runner: `scripts/p6-acceptance.sh` /
+  `backend/scripts/p6-acceptance.mjs` (+unit test `scripts/test-p6-acceptance.sh`).
+- **Manual acceptance:** PENDING — walkthrough section P6 in `docs/testing/p2-p6-manual-verification.md`.
+
 ### P2 host preprocessing CLI — implementation complete, automated PASS, manual PENDING (2026-08-11)
 
 - **Scope:** P2 (PRD D2, based on the P1.1 registry contract): the installed native `thothctl`