feat(context): reasoning-thread continuity, L3 doc filtering, and gate hardening

Threads reasoning_content across inference calls and journal renders, filters
markdown noise out of L3 repo-knowledge retrieval, adds PlanLinter H3 checks,
and tightens filesystem tool output/dir-listing behavior surfaced by prior
live QA (see project_readloop_campaign memory).

apps/tui-go/internal/app/model.go

@@ -89,6 +89,22 @@ type EventEntry struct {
 	Detail string
 }
 
+// PlanStageStatus tracks a stage's lifecycle in a locked execution plan.
+type PlanStageStatus int
+
+const (
+	PlanPending   PlanStageStatus = iota
+	PlanRunning
+	PlanCompleted
+	PlanFailed
+)
+
+// PlanStage is one stage in a locked execution plan, with live execution status.
+type PlanStage struct {
+	ID     string
+	Status PlanStageStatus
+}
+
 // ToolStatus mirrors the Kotlin ToolDisplayStatus.
 type ToolStatus int
 
@@ -194,6 +210,8 @@ type Session struct {
 	Name               string
 	LastEventAt        int64
 	CurrentStage       string
+	PlanGoal           string
+	PlanStages         []PlanStage
 	WorkspaceRoot      string // bound cwd, from session.workspace_bound
 	LastOutput         string
 	LastResponse       string