feat(FN-4915): complete Step 5-7 — document taxonomy and ship changeset

Fusion-Task-Id: FN-4915
Fusion-Task-Lineage: d5c49dae-6069-4998-b632-aca52cc312dc

.changeset/fn-4915-secret-audit-taxonomy.md

@@ -0,0 +1,5 @@
+---
+"@runfusion/fusion": patch
+---
+
+Expand secret audit taxonomy and harden secret audit payload handling. This adds typed secret mutation coverage (`secret:create`, `secret:update`, `secret:delete`, `secret:read`, approval events, sync events, and env lifecycle events), introduces plaintext-forbidden metadata enforcement via `assertNoSecretPlaintext`, adds non-blocking `SecretsStore` audit emitter hooks for CRUD/read operations, and ensures secret audit emission paths avoid leaking plaintext/ciphertext/nonce fields.

AGENTS.md

@@ -331,7 +331,7 @@ Reusable quality gates at configurable lifecycle phases. **Pre-merge** can block
 Every engine mutation is recorded across four domains:
 - **Database** — task:create, task:update, task:move, `room:ambiguity:branch` (deictic message routing telemetry), etc.
 - **Git** — worktree:create, commit:create, merge:resolve, etc.
-- **Filesystem** — file:write, prompt:write, attachment:create, `secret:env-*`, etc.
+- **Filesystem** — file:write, prompt:write, attachment:create, `secret:read|create|update|delete|approval-requested|approval-granted|approval-denied|sync-push|sync-pull`, `secret:env-*`, etc.
 - **Sandbox** — `sandbox:prepare`, `sandbox:run`, `sandbox:failure`, `sandbox:fallback`.
 
 Events are tied to run IDs end-to-end. See [docs/architecture.md](./docs/architecture.md) for the audit API.

docs/secrets.md

@@ -129,16 +129,29 @@ Audit payloads exclude plaintext values, passphrases, and envelope crypto materi
 
 ## Audit Events
 
-Current run-audit docs already list filesystem secret env lifecycle event names:
+Filesystem-domain secret audit taxonomy:
 
+- `secret:read`
+- `secret:create`
+- `secret:update`
+- `secret:delete`
+- `secret:approval-requested`
+- `secret:approval-granted`
+- `secret:approval-denied`
+- `secret:sync-push`
+- `secret:sync-pull`
 - `secret:env-write`
 - `secret:env-write-skipped`
 - `secret:env-cleanup`
 - `secret:env-cleanup-skipped`
 
-⚠️ The broader secret event taxonomy (`secret:create`, `secret:update`, `secret:delete`, `secret:read`, approvals, sync push/pull) is not wired in this branch. Follow-up: **FN-4867**.
+Wired in this branch/task lineage: `secret:read`, `secret:create`, `secret:update`, `secret:delete`, and approval events (`secret:approval-requested`, `secret:approval-granted`, `secret:approval-denied`).
 
-Rule that will continue to apply when read events land: secret-read audit records must never include plaintext values.
+Pending follow-ups:
+- Sync endpoint/event integration details continue under **FN-4913** (`secret:sync-push`, `secret:sync-pull`).
+- Env materialization lifecycle wiring continues under **FN-4912** (`secret:env-*`).
+
+**Plaintext prohibition:** audit payload metadata must never include plaintext, decrypted values, ciphertext, or nonce fields. Use `assertNoSecretPlaintext(...)` as the canonical enforcement helper before emitting secret audit events.
 
 ## Operational Notes