feat(x_search): gated X (Twitter) search tool with OAuth-or-API-key auth (#26763)

* feat(x_search): gated X (Twitter) search tool with OAuth-or-API-key auth

Salvages tools/x_search_tool.py from the closed PR #10786 (originally by
@Jaaneek) and reworks its credential resolution so the tool registers
when EITHER xAI credential path is available:

* XAI_API_KEY (paid xAI API key) is set in ~/.hermes/.env or the env, OR
* The user is signed in via xAI Grok OAuth — SuperGrok subscription —
  i.e. hermes auth add xai-oauth has been run

Both paths route through xAI's built-in x_search Responses tool at
https://api.x.ai/v1/responses. When both credentials exist OAuth wins,
matching tools/xai_http.py's existing preference order (uses SuperGrok
quota instead of paid API spend).

The check_fn calls resolve_xai_http_credentials() which auto-refreshes
the OAuth access token if it's within the refresh skew window, so a
True return means the bearer is fetchable AND non-empty.

Wiring
- tools/x_search_tool.py — new tool, ~370 LOC. Schema gated by check_fn,
  bearer resolved per-call so revoked OAuth surfaces a clean tool_error
  rather than an HTTP 401.
- toolsets.py — "x_search" toolset def. NOT added to _HERMES_CORE_TOOLS;
  users opt in via hermes tools.
- hermes_cli/tools_config.py — CONFIGURABLE_TOOLSETS entry + TOOL_CATEGORIES
  block with two provider options (OAuth + API key) sharing the existing
  xai_grok post_setup hook for credential bootstrap.
- hermes_cli/config.py — DEFAULT_CONFIG["x_search"] with model /
  timeout_seconds / retries. Additive nested key; no version bump.
- tests/tools/test_x_search_tool.py — 13 tests covering HTTP shape,
  handle validation, citation extraction, 4xx/5xx/timeout handling,
  and the full credential-resolution matrix (OAuth-only, API-key-only,
  both-set, neither-set, resolver-raises, config overrides, registry
  registration).
- website/docs/guides/xai-grok-oauth.md — adds X Search to the
  direct-to-xAI tools section with off-by-default note.
- website/docs/user-guide/features/tools.md — new row in the tools table.

Off by default — users enable via `hermes tools` → 🐦 X (Twitter) Search.
Schema only appears to the model when xAI credentials are configured.

Co-authored-by: Jaaneek <Jaaneek@users.noreply.github.com>

* docs(x_search): add dedicated feature page + reference entries

- website/docs/user-guide/features/x-search.md (new) — full feature
  walkthrough: authentication, enablement, configuration, parameters,
  returned fields, example, troubleshooting, see-also links.
- website/docs/reference/tools-reference.md — new "x_search" toolset
  section with parameter docs and credential gating note.
- website/docs/reference/toolsets-reference.md — new row in the
  toolset catalog table.
- website/sidebars.ts — wires the new feature page under
  Media & Web, after web-search.

---------

Co-authored-by: Jaaneek <Jaaneek@users.noreply.github.com>

website/sidebars.ts

@@ -83,6 +83,7 @@ const sidebars: SidebarsConfig = {
           items: [
             'user-guide/features/voice-mode',
             'user-guide/features/web-search',
+            'user-guide/features/x-search',
             'user-guide/features/browser',
             'user-guide/features/computer-use',
             'user-guide/features/vision',