fix(boot): isolate connector startup failures

[corylanou]

Summary

• keep Detent serving while connector creation or provisioning failures degrade only the affected project
• retry transient connector startup failures in-process with bounded exponential backoff, jitter, cancellation, and shutdown joining
• expose per-project connector state, last error, retry deadline, and terminal policy through snapshots and /health

Fixes #1483

UI Surface Contract

• N/A; this PR adds project health data without changing dashboard layout, density, or responsive visibility.
• This PR does not add persistent top-of-screen messaging.
• N/A; there are no visual changes to primary operator screens.

Test Plan

• make check
• focused race tests for project retry, reconciliation, supervised boot, snapshot, and health behavior
• regression tests for transient provisioning/factory failures, bounded jittered backoff, unaffected projects, permanent failures, and runtime survival

[chatgpt-codex-connector]

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