fix(#2618): thread --ws through query dispatch and sync root STATE.md on workstream.set (#2627)

* fix(#2618): thread --ws through query dispatch for state and init handlers

Gap 1 of #2618: the query dispatcher already accepts a workstream via
registry.dispatch(cmd, args, projectDir, ws), but several handlers drop it
before reaching planningPaths() / getMilestoneInfo() / findPhase() — so
stateJson and the init.* handlers return root-scoped results even when --ws
is provided.

Changes:

- sdk/src/query/state.ts: forward workstream into getMilestoneInfo() and
  extractCurrentMilestone() so buildStateFrontmatter resolves milestone data
  from the workstream ROADMAP/STATE instead of the root mirror.
- sdk/src/query/init.ts: thread workstream through initExecutePhase,
  initPlanPhase, initPhaseOp, and getPhaseInfoWithFallback (which fans out
  to findPhase() and roadmapGetPhase()). Also switch hardcoded
  join(projectDir, '.planning') to relPlanningPath(workstream) so returned
  state_path/roadmap_path/config_path reflect the workstream layout.

Regression test: stateJson with --ws workstream reads STATE.md from
.planning/workstreams/<name>/ when workstream is provided.

Closes #2618 (gap 1)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* fix(#2618): sync root .planning/STATE.md mirror on workstream.set

Gap 2 of #2618: setActiveWorkstream only flips the active-workstream
pointer file; the root .planning/STATE.md mirror stays stale. Downstream
consumers (statusline, gsd-sdk query progress, any tool that reads the
root STATE.md) continue to see the previous workstream's state.

After setActiveWorkstream(), copy .planning/workstreams/<name>/STATE.md
verbatim to .planning/STATE.md via writeFileSync. The workstream STATE.md
is authoritative; the root file is a pass-through mirror. Missing source
STATE.md is a no-op rather than an error — a freshly created workstream
with no STATE.md yet should still activate cleanly.

The response now includes `mirror_synced: boolean` so callers can
observe whether the root mirror was updated.

Regression test: workstreamSet root STATE.md mirror sync — switches
from a stale root mirror to a workstream STATE.md with different
frontmatter and asserts the root file now matches.

Closes #2618 (gap 2)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

sdk/src/query/workstream.ts

@@ -189,6 +189,25 @@ export const workstreamCreate: QueryHandler = async (args, projectDir) => {
   };
 };
 
+/**
+ * Rewrite the root `.planning/STATE.md` to mirror the active workstream's STATE.md.
+ *
+ * Fixes #2618 gap 2 — downstream consumers (statusline, progress, any tool that
+ * reads the root mirror) must see the new workstream's state immediately after a
+ * switch. The workstream STATE.md is authoritative; the root file is a
+ * pass-through copy. We write content verbatim (atomic write via writeFileSync)
+ * so frontmatter fields and body stay in lockstep with the source.
+ */
+function syncRootStateMirror(projectDir: string, name: string): void {
+  const wsStatePath = join(workstreamsDir(projectDir), name, 'STATE.md');
+  const rootStatePath = join(planningRoot(projectDir), 'STATE.md');
+  if (!existsSync(wsStatePath)) return;
+  try {
+    const content = readFileSync(wsStatePath, 'utf-8');
+    writeFileSync(rootStatePath, content, 'utf-8');
+  } catch { /* best-effort mirror; do not fail the switch */ }
+}
+
 export const workstreamSet: QueryHandler = async (args, projectDir) => {
   const name = args[0];
 
@@ -211,7 +230,8 @@ export const workstreamSet: QueryHandler = async (args, projectDir) => {
   }
 
   setActiveWorkstream(projectDir, name);
-  return { data: { active: name, set: true } };
+  syncRootStateMirror(projectDir, name);
+  return { data: { active: name, set: true, mirror_synced: existsSync(join(wsDir, 'STATE.md')) } };
 };
 
 export const workstreamStatus: QueryHandler = async (args, projectDir) => {