docs: add session naming documentation across all doc files

- website/docs/user-guide/sessions.md: New 'Session Naming' section
  with /title usage, title rules, auto-lineage, gateway support.
  Updated 'Resume by Name' section, 'Rename a Session' subsection,
  updated sessions list output format, updated DB schema description.
- website/docs/reference/cli-commands.md: Added -c "name" and
  --resume by title to Core Commands, sessions rename to Sessions
  table, /title to slash commands.
- website/docs/user-guide/cli.md: Added -c "name" and --resume by
  title to resume options.
- AGENTS.md: Added -c, --resume, sessions list/rename to CLI commands
  table. Added hermes_state.py to project structure.
- CONTRIBUTING.md: Updated hermes_state.py and session persistence
  descriptions to mention titles.
- hermes_cli/main.py: Fixed sessions help string to include 'rename'.

AGENTS.md

@@ -58,6 +58,7 @@ hermes-agent/
 ├── skills/               # Bundled skill sources
 ├── optional-skills/      # Official optional skills (not activated by default)
 ├── cli.py                # Interactive CLI orchestrator (HermesCLI class)
+├── hermes_state.py       # SessionDB — SQLite session store (schema, titles, FTS5 search)
 ├── run_agent.py          # AIAgent class (core conversation loop)
 ├── model_tools.py        # Tool orchestration (thin layer over tools/registry.py)
 ├── toolsets.py           # Tool groupings
@@ -226,6 +227,9 @@ The unified `hermes` command provides all functionality:
 |---------|-------------|
 | `hermes` | Interactive chat (default) |
 | `hermes chat -q "..."` | Single query mode |
+| `hermes -c` / `hermes --continue` | Resume the most recent session |
+| `hermes -c "my project"` | Resume a session by name (latest in lineage) |
+| `hermes --resume <session_id>` | Resume a specific session by ID or title |
 | `hermes -w` / `hermes --worktree` | Start in isolated git worktree (for parallel agents) |
 | `hermes setup` | Configure API keys and settings |
 | `hermes config` | View current configuration |
@@ -240,6 +244,8 @@ The unified `hermes` command provides all functionality:
 | `hermes gateway` | Start gateway (messaging + cron scheduler) |
 | `hermes gateway setup` | Configure messaging platforms interactively |
 | `hermes gateway install` | Install gateway as system service |
+| `hermes sessions list` | List past sessions (title, preview, last active) |
+| `hermes sessions rename <id> <title>` | Rename/title a session |
 | `hermes cron list` | View scheduled jobs |
 | `hermes cron status` | Check if cron scheduler is running |
 | `hermes version` | Show version info |