feat: add /recap slash command — summarize recent session activity

Inspired by Claude Code's /recap (v2.1.114, April 2026). Produces a
compact text summary of recent activity in the current session:
turn counts, tools used, files touched, last user ask, and last
assistant reply. Useful when juggling multiple sessions or
returning to a session after being away.

Implementation notes:
- Pure local computation from the in-memory conversation history /
  gateway transcript. No LLM call, no auxiliary model, no prompt-cache
  invalidation — a recap should be instant and free.
- Works unchanged on CLI and every gateway platform (Telegram,
  Discord, Slack, …) via a shared hermes_cli.session_recap.build_recap
  helper. Claude Code only ships this on the CLI.
- Tailored to hermes-agent's tool vocabulary: file-editing tools
  (patch, write_file, read_file, skill_manage, skill_view) surface
  touched paths; tool-call counts highlight which classes of work
  drove the session.
- Added to ACTIVE_SESSION_BYPASS_COMMANDS and the Level-2 early
  intercept in gateway/run.py so /recap works while an agent is
  running (read-only, safe).

Source: https://code.claude.com/docs/en/whats-new/2026-w17

website/docs/reference/slash-commands.md

@@ -24,6 +24,7 @@ Type `/` in the CLI to open the autocomplete menu. Built-in commands are case-in
 | `/new` (alias: `/reset`) | Start a new session (fresh session ID + history) |
 | `/clear` | Clear screen and start a new session |
 | `/history` | Show conversation history |
+| `/recap` | Compact summary of recent session activity (turn counts, tools used, files touched, last ask/reply). Purely local; no LLM call or token cost. Works in CLI and on every gateway platform. Inspired by Claude Code's `/recap`. |
 | `/save` | Save the current conversation |
 | `/retry` | Retry the last message (resend to agent) |
 | `/undo` | Remove the last user/assistant exchange |