Drop the Action Cable workarounds the client now handles

[monorkin]

Picks up the Action Cable client's new lifecycle API (basecamp/actioncable-go#6 and #7) and drops the code here that was working around its silence.

• Dial no longer closes a client behind its own error. A Connect that gives up now stops the client itself. Dial bounds the opening with its own timeout rather than leaving a caller who passed no deadline inside the retry loop for good.
• A dial's credentials are fetched once. The pre-flight authHeader call is gone: an error from building the upgrade request now comes back wrapped in the one Connect returns, so a token that can't be built is reported instead of retried out of sight.
• Client.Err says whether the shared TUI connection stopped, and why. That replaces calling Connect a second time and reading ErrAlreadyConnected as a sign of life. It also fixes a real case the probe got wrong: a rejected subscription would report a non-ErrAlreadyConnected error and condemn a connection the other watches were still using.
• Subscription.Err says why the messages dried up, in place of the atomic.Bool that OnRejected used to set, and hey watch now reports what actually ended it.
• Unsubscribe takes no context, so the goodbye no longer needs one built to outlive the watch that just ended.

One thing that stays

The Screener's separate reconnect channel. Its relay closes the channel when the watch's context ends, while the subscription behind it stays registered until the deferred goodbye, so a late callback would still write to a closed channel and panic off a goroutine Bubble Tea can't recover. That was never about the dispatcher draining callbacks after a stop, which is what its comment claimed — the comment is corrected here.

Checks

make check and make race-test both pass. The new test for the live-client path was mutation-checked: it fails when subscribeTuiCable treats a rejection as terminal.

[Copilot]

🟢 Approval recommended

The lifecycle migration matches the updated dependency contracts and includes focused regression coverage.

Pull request overview

Adopts Action Cable’s lifecycle APIs and removes local connection-state workarounds.

Changes:

• Uses Client.Err, Subscription.Err, and context-free Unsubscribe.
• Bounds initial cable connections and preserves underlying errors.
• Adds regression coverage for rejected subscriptions on live shared clients.

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File summaries

File	Description
internal/cmd/watch.go	Reports subscription termination through Subscription.Err.
internal/cmd/watch_test.go	Tests interruption, closure, and rejection outcomes.
internal/cmd/watch_calendar.go	Updates subscription teardown API usage.
internal/cmd/tui_watch.go	Uses native client lifecycle state and teardown.
internal/cmd/tui_watch_test.go	Covers rejection without discarding a live client.
internal/cable/cable.go	Bounds connection opening and relies on client cleanup.
internal/cable/cable_test.go	Verifies credential and failed-dial behavior.
go.mod / go.sum	Updates actioncable-go to the required revision.

Review details

• Files reviewed: 8/9 changed files
• Comments generated: 0
• Review effort level: Balanced

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