feat: transport registry and onboarding updates (#69)

docs/developing.md

@@ -77,12 +77,25 @@ Defines `Transport`, `MessageRef`, `RenderedMessage`, and `SendOptions`.
 
 Defines a renderer that converts `ProgressState` into `RenderedMessage` outputs.
 
+### `transports.py` - Transport registry
+
+Defines the transport backend protocol, registry helpers, and built-in transport registration.
+
+### `config_migrations.py` - Config migrations
+
+Applies one-time edits to on-disk config (e.g., legacy Telegram key migration) before
+`TakopiSettings` validation runs.
+
+### `telegram/backend.py` - Telegram transport backend
+
+Adapter that validates Telegram config, runs onboarding, and builds/runs the Telegram bridge.
+
 ### `cli.py` - CLI entry point
 
 | Component | Purpose |
 |-----------|---------|
 | `run()` / `main()` | Typer CLI entry points |
-| `_parse_bridge_config()` | Reads config + builds `TelegramBridgeConfig` + `ExecBridgeConfig` |
+| `_run_auto_router()` | Loads settings, resolves transport + engine, builds router, delegates to transport backend |
 
 ### `progress.py` - Progress tracking
 
@@ -261,6 +274,7 @@ Environment flags:
 - `PI_CODING_AGENT_DIR` (override Pi agent session directory base path)
 
 CLI flag: `--debug` enables debug logging (overrides `TAKOPI_LOG_LEVEL`).
+CLI flag: `--transport <id>` overrides the configured transport backend.
 
 ### `telegram/onboarding.py` - Setup validation
 

docs/projects.md

@@ -20,7 +20,7 @@ All config lives in `~/.takopi/takopi.toml`.
 ```toml
 default_engine = "codex"       # optional
 default_project = "z80"        # optional
-transport = "telegram"         # required
+transport = "telegram"         # optional, defaults to "telegram"
 
 [transports.telegram]
 bot_token = "..."              # required
@@ -33,6 +33,9 @@ default_engine = "codex"       # optional, per-project override
 worktree_base = "master"       # optional, base for new branches
 ```
 
+Legacy config note: top-level `bot_token` / `chat_id` are auto-migrated into
+`[transports.telegram]` on startup.
+
 Note on `worktrees_dir`:
 
 - The default `.worktrees` lives inside the repo root. You'll see it as an
@@ -49,6 +52,7 @@ Validation rules:
 - `default_project` must match a configured project alias.
 - Project aliases cannot collide with engine ids or reserved commands (`/cancel`).
 - `default_engine` and per-project `default_engine` must be valid engine ids.
+- `transport` defaults to `"telegram"` when omitted; override per-run with `--transport`.
 
 ## `takopi init`