docs(FN-4492): complete Step 1 — define UX progression

Fusion-Task-Id: FN-4492
Fusion-Task-Lineage: a358eab9-8491-41ef-9713-75961eb41d5d

docs/dag/milestone-c-dashboard-plan.md

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+# Milestone C: DAG dashboard surfacing plan
+
+Related tasks: **FN-4487**, **FN-4471**, **FN-4490**, **FN-4491**, **FN-4492**.
+
+## Constraints & Governance
+
+> "Do not file, plan, or implement tasks that adjust button mobile-responsiveness, touch-target sizing, or mobile reflow of header/action button rows anywhere in the dashboard (TaskCard, SettingsModal, ChatView, MissionManager, AgentsView, FAB, etc.). **Keep buttons as they are.**"
+
+> "Reliability mechanism changes are currently under freeze pending FN-4359 governance hardening; treat new reliability-layer behavior changes as blocked unless explicitly approved in task scope."
+
+This document is planning-only. No runtime behavior, scheduler/executor/merger code, dashboard routes, API endpoints, or schema changes are made here.
+
+## UX Progression (debug → operator)
+
+### Stage 1 — Debug surface
+
+**Audience:** Fusion developers debugging prototype orchestration.
+
+**Ship:** Read-only structured-log view for `[dag-coordinator]` events, filterable by `runId`, mirroring `AgentLogViewer` / `ActivityFeed` interaction patterns.
+
+**Operator questions answered:**
+- Did this DAG run start and finish/abort?
+- Which node was enqueued/completed/failed most recently?
+- What failure reason code was emitted for the failing node/run?
+
+**Events consumed from FN-4490 contract:**
+- `dag:run:start`
+- `dag:node:enqueue`
+- `dag:node:complete`
+- `dag:node:fail`
+- `dag:run:complete`
+- `dag:run:abort`
+
+### Stage 2 — Run inspector
+
+**Audience:** Power users monitoring multi-task DAG runs.
+
+**Ship:** Per-run detail inspector with node table, dependency/blocked context, and task deep-links into `TaskDetailModal`; read-only.
+
+**Operator questions answered:**
+- Which DAG node failed and why?
+- Which nodes are complete vs still pending/in-progress?
+- Which Fusion task corresponds to each node and where do I inspect logs/details?
+
+**Events consumed from FN-4490 contract:**
+- `dag:run:start`
+- `dag:node:enqueue`
+- `dag:node:complete`
+- `dag:node:fail`
+- `dag:run:complete`
+- `dag:run:abort`
+
+### Stage 3 — Operator surface
+
+**Audience:** End-users orchestrating DAG runs.
+
+**Ship:** Top-level run list, per-run graph visualization (nodes + edges), run-state summary, and pause/resume/cancel controls.
+
+**Operator questions answered:**
+- Is this run still making progress or stalled?
+- Which branch/path of the graph failed and what is downstream impact?
+- Can I safely pause/resume/cancel without violating task ownership or merge safety?
+
+**Events consumed from FN-4490 contract:**
+- `dag:run:start`
+- `dag:node:enqueue`
+- `dag:node:complete`
+- `dag:node:fail`
+- `dag:run:complete`
+- `dag:run:abort`
+
+#### Events to add in FN-4490 follow-up
+
+Stage 3 controls need explicit pause/resume observability. FN-4490 currently defines only `dag:run:abort` (not pause/resume), so add:
+- `dag:run:pause`
+- `dag:run:resume`
+
+These are follow-up requirements and are not introduced as implemented behavior in this task.