Sync docs and fix flaky renewal e2e test

- ARCHITECTURE.md: add Vault Endpoints section, /unseal UI page,
  vault_sealed/vault_unsealed audit events, sealed interceptor in
  gRPC chain
- openapi.yaml: add /v1/vault/{status,unseal,seal} endpoints, update
  /v1/health sealed-state docs, add VaultSealed response component,
  add vault audit event types and Admin — Vault tag
- web/static/openapi.yaml: kept in sync with root
- test/e2e: increase renewal test token lifetime from 2s to 10s
  (sleep 6s) to eliminate race between token expiry and HTTP round-trip

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

openapi.yaml

@@ -307,6 +307,18 @@ components:
             error: rate limit exceeded
             code: rate_limited
 
+    VaultSealed:
+      description: |
+        The vault is sealed. The server is running but has no key material.
+        Unseal via `POST /v1/vault/unseal` before retrying.
+      content:
+        application/json:
+          schema:
+            $ref: "#/components/schemas/Error"
+          example:
+            error: vault is sealed
+            code: vault_sealed
+
 paths:
 
   # ── Public ────────────────────────────────────────────────────────────────
@@ -314,12 +326,17 @@ paths:
   /v1/health:
     get:
       summary: Health check
-      description: Returns `{"status":"ok"}` if the server is running. No auth required.
+      description: |
+        Returns server health status. Always returns HTTP 200, even when the
+        vault is sealed. No auth required.
+
+        When the vault is sealed, `status` is `"sealed"` and most other
+        endpoints return 503. When healthy, `status` is `"ok"`.
       operationId: getHealth
       tags: [Public]
       responses:
         "200":
-          description: Server is healthy.
+          description: Server is running (check `status` for sealed state).
           content:
             application/json:
               schema:
@@ -327,6 +344,7 @@ paths:
                 properties:
                   status:
                     type: string
+                    enum: [ok, sealed]
                     example: ok
 
   /v1/keys/public:
@@ -369,6 +387,121 @@ paths:
                     description: Base64url-encoded public key bytes.
                     example: 11qYAYKxCrfVS_7TyWQHOg7hcvPapiMlrwIaaPcHURo
 
+  /v1/vault/status:
+    get:
+      summary: Vault seal status
+      description: |
+        Returns whether the vault is currently sealed. Always accessible,
+        even when sealed. No auth required.
+
+        Clients should poll this after startup or after a 503 `vault_sealed`
+        response to determine when to attempt an unseal.
+      operationId: getVaultStatus
+      tags: [Public]
+      responses:
+        "200":
+          description: Current vault seal state.
+          content:
+            application/json:
+              schema:
+                type: object
+                required: [sealed]
+                properties:
+                  sealed:
+                    type: boolean
+                    example: false
+
+  /v1/vault/unseal:
+    post:
+      summary: Unseal the vault
+      description: |
+        Provide the master passphrase to derive the encryption key, decrypt
+        the Ed25519 signing key, and unseal the vault. Once unsealed, all
+        other endpoints become available.
+
+        Rate limited to 3 requests per second per IP (burst 5) to limit
+        brute-force attempts against the passphrase.
+
+        The passphrase is never logged. A generic `"unseal failed"` error
+        is returned for any failure (wrong passphrase, vault already unsealed
+        mid-flight, etc.) to avoid leaking information.
+      operationId: unsealVault
+      tags: [Public]
+      requestBody:
+        required: true
+        content:
+          application/json:
+            schema:
+              type: object
+              required: [passphrase]
+              properties:
+                passphrase:
+                  type: string
+                  description: Master passphrase used to derive the encryption key.
+                  example: correct-horse-battery-staple
+      responses:
+        "200":
+          description: Vault unsealed (or was already unsealed).
+          content:
+            application/json:
+              schema:
+                type: object
+                properties:
+                  status:
+                    type: string
+                    enum: [unsealed, already unsealed]
+                    example: unsealed
+        "400":
+          $ref: "#/components/responses/BadRequest"
+        "401":
+          description: Wrong passphrase or key decryption failure.
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/Error"
+              example:
+                error: unseal failed
+                code: unauthorized
+        "429":
+          $ref: "#/components/responses/RateLimited"
+
+  /v1/vault/seal:
+    post:
+      summary: Seal the vault (admin)
+      description: |
+        Zero all key material in memory and transition the server to the
+        sealed state. After this call:
+
+        - All subsequent requests (except health, vault status, and unseal)
+          return 503 `vault_sealed`.
+        - The caller's own JWT is immediately invalidated because the public
+          key needed to verify it is no longer held in memory.
+        - The server can be unsealed again via `POST /v1/vault/unseal`.
+
+        This is an emergency operation. Use it to protect key material if a
+        compromise is suspected. It does **not** restart the server or wipe
+        the database.
+      operationId: sealVault
+      tags: [Admin — Vault]
+      security:
+        - bearerAuth: []
+      responses:
+        "200":
+          description: Vault sealed (or was already sealed).
+          content:
+            application/json:
+              schema:
+                type: object
+                properties:
+                  status:
+                    type: string
+                    enum: [sealed, already sealed]
+                    example: sealed
+        "401":
+          $ref: "#/components/responses/Unauthorized"
+        "403":
+          $ref: "#/components/responses/Forbidden"
+
   /v1/auth/login:
     post:
       summary: Login
@@ -1148,7 +1281,7 @@ paths:
         `pgcred_accessed`, `pgcred_updated`, `pgcred_access_granted`,
         `pgcred_access_revoked`, `tag_added`, `tag_removed`,
         `policy_rule_created`, `policy_rule_updated`, `policy_rule_deleted`,
-        `policy_deny`.
+        `policy_deny`, `vault_sealed`, `vault_unsealed`.
       operationId: listAudit
       tags: [Admin — Audit]
       security:
@@ -1530,3 +1663,5 @@ tags:
     description: Requires admin role.
   - name: Admin — Policy
     description: Requires admin role. Manage policy rules and account tags.
+  - name: Admin — Vault
+    description: Requires admin role. Emergency vault seal operation.