feat: add bridge dev command that runs devCommand under health supervision

[vercel-eddie]

Summary

Adds bridge dev <bridge> that launches the devCommand from devcontainer.json (e.g. "pnpm dev"), streams its output, and waits until the source deployment's probes report the local app healthy. PID is persisted across invocations so re-running cleanly kills the previous server.

$ bridge dev api-devbox
Started: pnpm dev (pid 12345)
Logs:    /Users/eddie/.bridge/logs/dev-api-devbox.log
Waiting for probes to report healthy...
┌── Running: pnpm dev ──┐
│ ▲ Next.js 14.x        │
│ ✓ Ready in 2.1s       │
└───────────────────────┘
✓ Healthy (pid 12345)

What's in this PR

bridge dev command — positional bridge name, --timeout (default 2m, BRIDGE_DEV_TIMEOUT).

• Reads devCommand from devcontainer.json (string or array)
• Starts the command via devcontainer exec with Setsid so it survives the CLI exit
• Streams the log file into the same interact.NewViewport bridge create uses
• Re-running kills the previously tracked PID first (SIGTERM with 3s grace → SIGKILL)
• Exit precedence: dev process exits → all probes pass → --timeout

Probe RPC on InterceptorService — synchronous, stateless "is the app responding right now?" check. Bypasses the threshold-tracked GetStatus view so a stale HEALTHY from a previous session can't fool the new run. Bridge dev polls Probe; bridge get keeps using GetStatus for the smoothed steady-state view.

bridge get APPLICATION column — new application_status field on GetCommandResponseBridge. Queried in parallel per bridge with a 1.5s timeout. Values: healthy / unhealthy / starting / unreachable / stopped. Defaults to healthy when the source has no probes.

--start-container / -s on bridge create — starts the devcontainer after creating the bridge but doesn't attach. --connect now implies --start-container. Useful for agent flows that want a container running without holding the terminal.

Install path moved to ~/.local/bin/bridge — no sudo, no xattr, no Gatekeeper workaround needed (curl doesn't quarantine its downloads). Override with BRIDGE_INSTALL_DIR=.... Hint about PATH is printed only when the directory isn't already on it.

linuxBinaryPath no longer dev-only-relative — prefers ~/.bridge/bin/bridge-linux when present so bridge create works from any CWD; falls back to ./dist/bridge-linux only for the in-repo development workflow.

Misc:

• Session proto extended with dev_pid / dev_started_at / dev_command
• session.Write(*Session) so callers can Load → mutate → Write without losing fields; Save still resets dev state on fresh creates
• PID is persisted regardless of dev-command outcome — agents/next runs can use it for diagnostics or cleanup even on a failed start

Tests

• pkg/probe/*_test.go — Probe interface contract, HTTP/TCP/Exec handlers
• pkg/devcontainer/devcommand_test.go — string / array / missing / invalid devCommand
• pkg/session/session_test.go — fresh save, full round-trip with dev fields, Save resets, idempotent Delete
• pkg/commands/dev_test.go — orchestrator state machine via fakeInterceptor (Probe shape now): immediate healthy, exit-wins-over-health, timeout, half-passing, no-probes-defaults-to-healthy, mid-wait healthy transition, context cancel, mid-wait exit
• Full unit suite + -race clean

🤖 Generated with Claude Code