feat(tui): opt-in auto-resume of the most recent session (#17130)

* feat(tui): opt-in auto-resume of the most recent session

`hermes --tui` always forges a fresh session at startup unless the user
sets `HERMES_TUI_RESUME=<id>`.  Disconnects, terminal-window crashes,
and accidental Ctrl+D therefore lose every piece of in-flight context
even though `state.db` still has the full history a `/resume` away.

Add an opt-in path that mirrors classic CLI's `hermes -c` muscle
memory: when `display.tui_auto_resume_recent: true` is set in
`~/.hermes/config.yaml`, the TUI looks up the most recent human-facing
session and resumes it instead of starting fresh.  Default off so
existing users aren't surprised; explicit `HERMES_TUI_RESUME` always
wins.

Wires:

* New `session.most_recent` JSON-RPC in `tui_gateway/server.py` that
  returns the first non-`tool` row from `list_sessions_rich`, or
  `{"session_id": null}` when none.  Uses the same deny-list as
  `session.list` so sub-agent rows can't sneak in.
* `createGatewayEventHandler.handleReady` re-ordered: explicit
  `STARTUP_RESUME_ID` first (unchanged), then conditional auto-resume
  via `config.get full → display.tui_auto_resume_recent`, then the
  legacy `newSession()` fallback.  Failures of either RPC fall back
  to `newSession()` so the path is always finite.
* Default `display.tui_auto_resume_recent: False` added to
  `DEFAULT_CONFIG` in `hermes_cli/config.py` (no `_config_version`
  bump per AGENTS.md — deep-merge handles the additive key).

Tests:

* 4 new vitest cases in `createGatewayEventHandler.test.ts` cover
  every gate-and-fallback combination (env wins, config off, config
  on with hit, config on with miss).
* 3 new pytest cases for `session.most_recent` (denied row skip,
  tool-only → null, db-unavailable → null).

Validation:
  scripts/run_tests.sh tests/test_tui_gateway_server.py — 93/93.
  cd ui-tui && npm run type-check — clean; npm test --run — 393/393.

* review(copilot): fold session.most_recent errors into null + extend ConfigDisplayConfig

* review(copilot): cover RPC-rejection fallbacks in auto-resume tests

hermes_cli/config.py

@@ -703,6 +703,11 @@ DEFAULT_CONFIG = {
         "personality": "kawaii",
         "resume_display": "full",
         "busy_input_mode": "interrupt",  # interrupt | queue | steer
+        # When true, `hermes --tui` auto-resumes the most recent human-
+        # facing session on launch instead of forging a fresh one.
+        # Mirrors `hermes -c` muscle memory.  Default off so existing
+        # users aren't surprised.  HERMES_TUI_RESUME=<id> always wins.
+        "tui_auto_resume_recent": False,
         "bell_on_complete": False,
         "show_reasoning": False,
         "streaming": False,