P4 core: broker-held app connections + gated, broker-executed Slack posting

- app_connections repo; POST /api/apps/connect (keys/basic): the credential
  goes to the secret broker over its socket and only the encrypted ref lands
  in the row; disconnect endpoint; /api/apps directory merged with live
  connection status; audit rows for connect/disconnect
- Broker protocol: InvokeHttp carries a JSON body
- slack.post tool (SendsExternally -> gated): marked broker_executed — the
  runtime skips its own grant consumption and the BROKER independently
  verifies + consumes the single-use grant, then calls Slack with the bot
  token injected; the runtime never sees the credential
- Config: [broker] socket_path + [slack] base_url; e2e harness spawns the
  real teamclaw-broker daemon and the server hosts an e2e-only /__slack sink
- SlackApp: Connection tab stores the token via the broker; connected state
- Integration test: blocked while pending -> approved -> sink received
  exactly one post with 'Bearer xoxb-test-token' -> grant replay refused
- E2E journey: connect Slack in the panel -> gated post card with preview ->
  sink empty while pending -> approve -> exactly one post, queue clear

133 Rust + 63 frontend tests + 21 Playwright journeys.

Co-Authored-By: Claude Fable 5 <[email protected]>

crates/tc-api/tests/claw_crud.rs

@@ -12,10 +12,7 @@ fn test_runtime(pool: sqlx::PgPool) -> tc_runtime::Runtime {
     tc_runtime::Runtime::new(
         pool,
         std::sync::Arc::new(tc_llm::ScriptedProvider::from_toml("").unwrap()),
-        tc_runtime::RuntimeConfig {
-            model: "scripted".into(),
-            max_tokens: 1024,
-        },
+        tc_runtime::RuntimeConfig::basic("scripted", 1024),
     )
 }