fix(leyline): configurable daemon-start timeout + crash-vs-timeout diagnostics (mache-0a1ded)

[jamestexas]

The bug

Auto-started leyline daemons failed with socket did not appear within 5s on cold starts — first run, arena init/enrichment setup, or contention with co-tenant daemons on the shared ~/.mache/default.arena (surfaced with ≥1 mache serve already live). Two root problems:

1. The 5s socket-appear wait was hardcoded and too short for a cold start.
2. A daemon that crashed on startup was still reported as a timeout — after a full 5s wait for a socket that could never appear.

Fix

• Configurable timeout via MACHE_LEYLINE_START_TIMEOUT (a Go duration like 30s, or a bare integer = seconds). Default raised 5s → 15s.
• Crash vs timeout: the poll loop now watches the spawned process. If it exits before the socket appears, return immediately with exited during startup: <exit status> instead of waiting out the timeout. The timeout error now names the contended arena and points at MACHE_LEYLINE_START_TIMEOUT.

Tests

• leylineStartTimeout env-parsing table (duration, bare-seconds, garbage/zero/negative fallback, whitespace) + a guard that the default stays ≥10s.
• The existing timeout test now uses a sleeper fake + MACHE_LEYLINE_START_TIMEOUT=1s — fast, and still exercises the real timeout path (previously a /bin/sh fake that exited immediately, which now correctly takes the crash branch).
• New crash-path test: a fast-exiting fake asserts exit-detection returns in <5s with the exited during startup message (not a timeout).

Not in scope (follow-up)

The cross-process arena isolation half of the contention story — two separate mache serve processes racing on the same ~/.mache/default.{arena,ctrl,sock} — is left for follow-up under mache-0a1ded / the mache-823d91 reliability half. This PR removes the spurious-timeout failures and makes the knob available.

Verification

• go test ./internal/leyline/ → ok (full package)
• go vet + golangci-lint (pre-commit) → pass

[github-actions]

find_smells (advisory)

Scoped to files changed in this PR. Rules below run on the standalone (no-LLO) cross-ref tables; _ast rules (cyclomatic_complexity, long_function, long_file, magic_int_in_comparison) are not exercised here.

fan_out_skew — 1 finding(s) in changed files

Source	Node	Metric
internal/leyline/socket.go	leyline/functions/DiscoverOrStart/source	33

Rules: the registry is cmd/smell_rules.go (source of truth); see the authoring guide to add one. Advisory only — these are heuristics, not gates.

[Copilot]

Pull request overview

This PR improves internal/leyline daemon auto-start reliability by making the startup socket wait configurable and by distinguishing between a daemon that is still initializing vs one that exited before binding its socket.

Changes:

• Add MACHE_LEYLINE_START_TIMEOUT parsing (Go duration or bare seconds) and raise the default startup wait to 15s.
• Detect “daemon exited during startup” by watching the spawned process while polling for the socket, returning immediately on exit.
• Update and add tests to cover env parsing, the real timeout path (fast with 1s), and the crash-during-startup path.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
internal/leyline/start_timeout_test.go	Adds table tests for timeout env parsing plus a guard on the default timeout.
internal/leyline/socket.go	Implements configurable startup timeout and crash-vs-timeout diagnostics during daemon auto-start.
internal/leyline/socket_test.go	Updates timeout-path test to use a sleeper fake with 1s timeout; adds a new crash-path test.

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