feat: per-job command timeout with global default

Add an optional per-job run timeout following the overlap_policy inherit
pattern: Job.TimeoutSeconds (0 = inherit) resolves against a new
Config.DefaultTimeoutSeconds (default 30s), replacing the hard-coded 30s
guard in runner.RunJob.

- domain/storage: new fields, default 30, load-time normalization
- runner: RunJob takes an explicit timeout; StartOnly stays untimed so it
  keeps measuring launch latency only
- app: effectiveTimeout resolves under mu into runEnv, threaded to runJob;
  seam signature and validation updated; DisplayTimeout helper
- ui: Timeout entry in the job dialog, Default timeout in Settings, and a
  Timeout row in the details panel
- tests + docs (ARCHITECTURE, STANDARDS, ROADMAP, CHANGELOG) updated;
  version bumped to 0.12.0

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/domain/job.go

@@ -6,13 +6,17 @@ package domain
 // separate JobRuntime so the jobs file stays a clean, hand-editable record of
 // configuration and never mixes in process-lifetime bookkeeping.
 type Job struct {
-	ID               int    `json:"id"`
-	Name             string `json:"name"`
-	Folder           string `json:"folder,omitempty"`
-	Schedule         string `json:"schedule"`
-	Command          string `json:"command"`
-	Arguments        string `json:"arguments,omitempty"`
-	StartOnly        bool   `json:"start_only,omitempty"`
-	Enabled          bool   `json:"enabled"`
-	OverlapPolicy    string `json:"overlap_policy,omitempty"`
+	ID            int    `json:"id"`
+	Name          string `json:"name"`
+	Folder        string `json:"folder,omitempty"`
+	Schedule      string `json:"schedule"`
+	Command       string `json:"command"`
+	Arguments     string `json:"arguments,omitempty"`
+	StartOnly     bool   `json:"start_only,omitempty"`
+	Enabled       bool   `json:"enabled"`
+	OverlapPolicy string `json:"overlap_policy,omitempty"`
+	// TimeoutSeconds bounds how long a run may take before it is killed. 0 means
+	// "inherit the global Config.DefaultTimeoutSeconds", mirroring OverlapPolicy:
+	// normalizeJobs must leave 0 untouched rather than backfilling the default.
+	TimeoutSeconds int `json:"timeout_seconds,omitempty"`
 }