Fix the flaky MCP naming suite and drop the unused CI job

[CountableNewt]

Three small, independent commits.

Fix the flaky McpToolNamingTests SQLite lock

withMcpToolNamingApp boots the full app through configure(app), which registers SkillUsageRetentionLifecycle. That handler's didBootAsync spawns a detached task running SkillUsageService.prune immediately — per-project DELETEs against the same shared in-memory SQLite database the suite is inserting into. Those deletes take a write lock concurrently with the suite's writes, which is the intermittent database is locked failure.

The two sibling suites that write telemetry already set DISABLE_SKILL_USAGE_RETENTION_SCHEDULER=1 (SkillUsageRouteTests, SkillUsageAnalyticsTests); this one didn't. Now it does.

Verified with 6 consecutive runs of swift test --filter McpToolNamingTests — all 6 tests green each run. The flake was intermittent, so that is corroboration rather than proof, but the racing writer is gone by construction.

Not addressed here: McpOAuthTests, ApiKeyRevocationTests, McpPingRouteTests, SecurityFindingMitigationTests, and SkillRuntimeHardeningTests boot the app the same way without that env var, so they carry the same latent race. Happy to follow up by either adding the var to each or gating the lifecycle off under .testing in one place.

Drop the unused changed-path detection job

The ci job never declared needs: changes and read none of the job's four outputs, so changes and scripts/ci-detect-changes.sh fed nothing. Path filtering now lives in each Railway service's watchPatterns. Removed the job, the script, and the stale references in README.md, AGENTS.md, and docs/test-plans/README.md. The workflow still parses to a single ci job with 3 steps.

Document the sleepApplication plan noise

Checked the live Gateway config in dev: deploy carries no sleepApplication key at all, even though the applied config declares false. Railway omits the field once app sleep is off, so railway config plan will report sleepApplication: null → false for Gateway and Web in both environments on every run. railway/README.md now calls that out as expected noise rather than a pending change.

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