feat: add Cisco IOS shell with mode state machine and abbreviation matching (PLAN.md 3.2)

Implements a Cisco IOS CLI emulator with four modes (user exec, privileged exec,
global config, interface config), Cisco-style command abbreviation (e.g. sh run,
conf t), enable password flow, and realistic show command output including
running-config, interfaces, IP routes, and VLANs.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

README.md

@@ -34,7 +34,7 @@ Key settings:
 - `auth.accept_after` — accept login after N failures per IP (default `10`)
 - `auth.credential_ttl` — how long to remember accepted credentials (default `24h`)
 - `auth.static_credentials` — always-accepted username/password pairs (optional `shell` field routes to a specific shell)
-- Available shells: `bash` (fake Linux shell), `fridge` (Samsung Smart Fridge OS), `banking` (80s-style bank terminal TUI), `adventure` (Zork-style text adventure dungeon)
+- Available shells: `bash` (fake Linux shell), `fridge` (Samsung Smart Fridge OS), `banking` (80s-style bank terminal TUI), `adventure` (Zork-style text adventure dungeon), `cisco` (Cisco IOS CLI with mode state machine and command abbreviation)
 - `storage.db_path` — SQLite database path (default `oubliette.db`)
 - `storage.retention_days` — auto-prune records older than N days (default `90`)
 - `storage.retention_interval` — how often to run retention (default `1h`)
@@ -91,7 +91,7 @@ Build a Docker image via nix:
 ```sh
 nix build .#dockerImage
 docker load < result
-docker run -v /path/to/data:/data -p 2222:2222 -p 8080:8080 oubliette:0.7.0
+docker run -v /path/to/data:/data -p 2222:2222 -p 8080:8080 oubliette:0.8.0
 ```
 
 Place your `oubliette.toml` in the data volume. The container exposes ports 2222 (SSH) and 8080 (web/metrics).