refactor(#1286): T4 — migrate 5 large destructure callers off the core spine (batch 3) (#1287)

Migrate the entire core surface of commands (~23 symbols), phase (~17),
roadmap, state, template to the leaf modules directly (behaviour-identical —
leaves are the objects core re-exports by reference). All 5 now import zero
core symbols and are removed from the allowlist (9 -> 4). Dropped a dead
`void replaceInCurrentMilestone` from phase.cts; stale core.cjs docstrings
fixed. core.cts re-exports untouched (serve the remaining 4 idiom-hard
files); teardown is T-final. No behaviour change.

Closes #1286

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

scripts/lint-core-spine-imports.allowlist.json

@@ -4,11 +4,6 @@
     "gsd-core/bin/gsd-tools.cjs",
     "src/audit-command-router.cts",
     "src/check-command-router.cts",
-    "src/commands.cts",
-    "src/intel-command-router.cts",
-    "src/phase.cts",
-    "src/roadmap.cts",
-    "src/state.cts",
-    "src/template.cts"
+    "src/intel-command-router.cts"
   ]
 }