feat(secrets): Bitwarden Secrets Manager integration with lazy bws install (#30035)

* feat(secrets): Bitwarden Secrets Manager integration with lazy bws install

Pull API keys from Bitwarden Secrets Manager at process startup
instead of storing them all in plaintext in ~/.hermes/.env.  One
bootstrap token (BWS_ACCESS_TOKEN) replaces N per-provider keys, and
rotating a credential becomes a single change in the Bitwarden web
app.

Bitwarden defaults to source of truth: secrets pulled from BSM
overwrite any matching env vars on startup so rotations actually
take effect.  Set secrets.bitwarden.override_existing: false in
config.yaml to invert.

The bws binary is auto-downloaded into ~/.hermes/bin/bws on first
use (pinned to v2.0.0, SHA-256 verified against the GitHub release
checksum file).  No apt, brew, or sudo required.

New surfaces:
  hermes secrets bitwarden setup    — interactive wizard
  hermes secrets bitwarden status   — config + binary + token state
  hermes secrets bitwarden sync     — dry-run fetch / --apply exports
  hermes secrets bitwarden disable  — flip enabled: false
  hermes secrets bitwarden install  — just download the binary

Failures (missing binary, bad token, no network) never block Hermes
startup — they emit a one-line warning to stderr and continue with
whatever credentials .env already had.

Docs: website/docs/user-guide/secrets/{index,bitwarden}.md
Tests: tests/test_bitwarden_secrets.py (26 tests, hermetic — bws
       subprocess and HTTP downloads fully mocked)

* chore(infographic): add bitwarden-secrets-manager bento-grid retro-pop-grid

Generated for PR #30035 — Bitwarden Secrets Manager integration.
Style picked via pick_pr_infographic_style.py rotation:
  layout: bento-grid
  style:  retro-pop-grid
  aspect: 1:1 square

Saved at infographic/bitwarden-secrets-manager/infographic.png

hermes_cli/config.py

@@ -1747,6 +1747,37 @@ DEFAULT_CONFIG = {
         "retries": 2,
     },
 
+    # =========================================================================
+    # External secret sources
+    # =========================================================================
+    # Pull credentials from external secret managers at process startup
+    # rather than storing them in ~/.hermes/.env.
+    "secrets": {
+        "bitwarden": {
+            # Master switch.  When false, BSM is never contacted and the
+            # bws binary is never auto-installed — same as not having
+            # this section at all.
+            "enabled": False,
+            # Name of the env var that holds the Bitwarden machine-account
+            # access token.  This is the one bootstrap secret; it lives
+            # in ~/.hermes/.env (or your shell) and never in config.yaml.
+            "access_token_env": "BWS_ACCESS_TOKEN",
+            # UUID of the BSM project to sync from.
+            "project_id": "",
+            # Seconds to cache fetched secrets in-process.  0 disables.
+            "cache_ttl_seconds": 300,
+            # When True, BSM values overwrite existing env vars.  Default
+            # True because the point of using BSM is centralized rotation —
+            # if .env had the final say, rotating in Bitwarden wouldn't
+            # take effect until you also cleared the matching .env line.
+            "override_existing": True,
+            # When True, the bws binary is auto-downloaded into
+            # ~/.hermes/bin/ on first use.  When False you must install
+            # bws yourself and have it on PATH.
+            "auto_install": True,
+        },
+    },
+
     # Config schema version - bump this when adding new required fields
     "_config_version": 23,
 }