Make the local connector easy to start and readable, and stop promptly

[MaggieAppleton]

Why

Maggie's real test on the #466 preview hit four problems.

• bun run connector failed with "script not found: connector" outside a Chopin checkout.
• The agent's permission prompts were opaque.
• A refused Build or Run answered with a silent 409.
• Ctrl-C took about 90 seconds to stop anything.

What changed

• One-line command that works anywhere. The connector is bundled into one file during bun run build and in the Docker image, and served at GET /connector.js with no auth and an ETag. The UI and docs give one command to run in the project folder:
  mkdir -p ~/.chopin && curl -fsSL {origin}/connector.js -o ~/.chopin/connector.js && CHOPIN_URL={origin} bun ~/.chopin/connector.js connect . -- copilot --acp --allow-all.
  bun run connector still works for contributors, and the bundle supports the stdio bridge mode.
• Readable terminal. Each job gets a styled header ("› Investigating …", "› Building …"), with plain finish and failure lines. A failure shows the tail of the agent's output. Permission prompts say what the agent wants to do and remember repeated answers.
• Clear not-connected note. A no-workspace refusal shows one shared note: the agent isn't connected, the command with Copy, that Bun is needed, and a "Trouble connecting?" link.
  • It appears in the investigation card.
  • It appears in Make Build plan explicit and show build status in one capsule #508's read-only Build view, for a refused Build plan or Retry, and for Build a delivered plan's later changes on demand without LIVE_BUILD #510's pressed Build of changes.
  • Other card refusals use plain copy.
• Ctrl-C stops promptly. Ctrl-C anywhere, including at a permission prompt, reports running work (builds, rebuilds, investigations, spikes) as stopped from the connector terminal, then disconnects. A second Ctrl-C exits at once.
• Server-side disconnect. disconnect_workspace now fails the connection's active builds and rebuilds immediately: persisted, then announced. The sweep still catches a connector killed without warning. Build's capsule and headline say why a build stopped.
• Process cleanup. When a job ends, the connector stops background processes left in its worktree, such as a dev server. A spike's throwaway worktree and branch are removed, and its pushes stay refused (Prototype uncertain passages inline before the first build (LIVE_SPIKES) #454).
• Troubleshooting docs. docs/local-experiments.md#trouble-connecting and docs/local-launcher.md now cover the downloadable connector and pairing problems.

sequenceDiagram
  participant P as Person
  participant C as Connector
  participant S as Chopin server
  participant B as Browser
  P->>C: Ctrl-C
  C->>C: abort the agent turn (also at a permission prompt)
  C->>S: report_implementation_build failed / fail_experiment<br/>"Stopped from the connector terminal."
  S->>S: persist the stopped build or run
  S-->>B: plan:implementation / experiment:changed
  C->>S: disconnect_workspace
  S->>S: fail remaining builds and rebuilds, interrupt runs (persisted)
  S-->>B: announce; capsule reads "Build stopped from the connector terminal"
  C->>C: stop agent process group and worktree processes, exit
  P->>C: second Ctrl-C exits at once

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Rebased onto the reworked stack

These five commits were rebased onto the updated #466 head.

• LocalAgentNote moved into Make Build plan explicit and show build status in one capsule #508's read-only Build view and Build a delivered plan's later changes on demand without LIVE_BUILD #510's rebuild refusal, and stays in the investigation card.
• disconnected() fits Keep a built document in sync with its pull requests (LIVE_BUILD) #452's rebuilds and the consent rules.
• The spike cleanup and no-push setup stay in the restyled run loop.
• The editor's inline-code style no longer leaks onto the command in a card.

Tests

• Connector unit tests for the output, the permission descriptions, process cleanup and the interrupt.
• A server test for GET /connector.js.
• Route tests that a disconnect fails a running build and a running rebuild.
• Model tests for endedReason.
• e2e for the Build and card notes, Copy and the troubleshooting link.
• bun run fix, bun run types, the full bun test, bun run ci, and the connector, experiments, implementation-launcher and harness e2e suites all pass locally.

Visuals

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