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/state.ts

@@ -38,7 +38,7 @@ export async function getMilestonePhaseFilter(projectDir: string, workstream?: s
   const milestonePhaseNums = new Set<string>();
   try {
     const roadmapContent = await readFile(planningPaths(projectDir, workstream).roadmap, 'utf-8');
-    const roadmap = await extractCurrentMilestone(roadmapContent, projectDir);
+    const roadmap = await extractCurrentMilestone(roadmapContent, projectDir, workstream);
     const phasePattern = /#{2,4}\s*Phase\s+([\w][\w.-]*)\s*:/gi;
     let m: RegExpExecArray | null;
     while ((m = phasePattern.exec(roadmap)) !== null) {
@@ -105,7 +105,7 @@ export async function buildStateFrontmatter(bodyContent: string, projectDir: str
   let milestone: string | null = null;
   let milestoneName: string | null = null;
   try {
-    const info = await getMilestoneInfo(projectDir);
+    const info = await getMilestoneInfo(projectDir, workstream);
     milestone = info.version;
     milestoneName = info.name;
   } catch { /* intentionally empty */ }