refactor: apply code-review findings to github-native coordination

scripts/github-coordination.js:
- parseArgs: replace 13-entry if/else chain with BOOL_FLAGS/VALUE_FLAGS
  lookup maps; shrinks from 119 to ~45 lines
- Extract dispatchCommand(options, ctx) and formatOutput(payload, options)
  from main(); main() shrinks to ~20 lines

scripts/lib/github-coordination.js:
- Split 1041-line monolith into 6 focused sub-modules under
  scripts/lib/github-coordination/ (policy, parsing, gh-api, state,
  actions, store); index becomes a thin re-export (~55 lines)
- Document ECC_GH_SHIM trust boundary in runGh() (gh-api.js)
- Document applyClaim() read→check→write race condition (actions.js)

tests/lib/github-coordination.test.js:
- Refactor runTests() to data-driven DESCRIPTORS array + runGroup()
  helper; runTests() shrinks to ~10 lines
- Add 5 new edge-case tests: normalizeRepo('') and normalizeRepo('   ')
  throw, desiredLabelsForState for blocked/ready statuses, and
  buildIssueStateFromAction for validate action (15 → 20 tests)

tests/scripts/github-coordination.test.js:
- Replace console.log in test runner with process.stdout.write

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

scripts/lib/github-coordination/parsing.js

@@ -0,0 +1,141 @@
+'use strict';
+
+const { DEFAULT_POLICY, DEFAULT_SCHEMA_VERSION, DEFAULT_SECTION_MARKER } = require('./policy');
+
+function escapeRegExp(str) {
+  return str.replace(/[.*+?^${}()|[\]\\]/g, '\\$&');
+}
+
+function normalizeBodyForComparison(body) {
+  return (body || '').replace(/lastSyncAt:\s*[^\n]+/g, 'lastSyncAt: NORMALIZED');
+}
+
+function extractCoordinationState(body, policy = DEFAULT_POLICY) {
+  const marker = escapeRegExp(policy.sectionMarker || DEFAULT_SECTION_MARKER);
+  const regex = new RegExp(
+    `<!--\\s*${marker}:start\\s*-->\\s*` +
+    '```json\\s*([\\s\\S]*?)\\s*```' +
+    `\\s*<!--\\s*${marker}:end\\s*-->`,
+    'm'
+  );
+  const match = String(body || '').match(regex);
+
+  if (!match) {
+    return null;
+  }
+
+  try {
+    const parsed = JSON.parse(match[1]);
+    return parsed && typeof parsed === 'object' ? parsed : null;
+  } catch (_error) {
+    return null;
+  }
+}
+
+function extractIssueReferences(text) {
+  const refs = new Set();
+  const source = String(text || '');
+  for (const match of source.matchAll(/(?:^|[^\d])#(\d+)\b/g)) {
+    refs.add(Number.parseInt(match[1], 10));
+  }
+  return Array.from(refs).filter(Number.isFinite).sort((a, b) => a - b);
+}
+
+function extractTasks(body) {
+  const lines = String(body || '').split(/\r?\n/);
+  const tasks = [];
+  let inTasks = false;
+
+  for (const rawLine of lines) {
+    const line = rawLine.trim();
+    if (/^#{2,3}\s+tasks\b/i.test(line) || /^#{2,3}\s+task list\b/i.test(line)) {
+      inTasks = true;
+      continue;
+    }
+    if (inTasks && /^#{2,3}\s+\S/.test(line)) {
+      break;
+    }
+    if (inTasks) {
+      const taskMatch = line.match(/^- \[( |x)\]\s+(.+)$/i);
+      if (taskMatch) {
+        tasks.push({
+          title: taskMatch[2].trim(),
+          done: taskMatch[1].toLowerCase() === 'x',
+        });
+      }
+    }
+  }
+
+  return tasks;
+}
+
+function parseStringList(value) {
+  if (!value) {
+    return [];
+  }
+  return String(value)
+    .split(',')
+    .map(part => part.trim())
+    .filter(Boolean);
+}
+
+function renderCoordinationState(state, policy = DEFAULT_POLICY) {
+  const marker = policy.sectionMarker || DEFAULT_SECTION_MARKER;
+  const payload = {
+    schemaVersion: state.schemaVersion || policy.schemaVersion || DEFAULT_SCHEMA_VERSION,
+    kind: state.kind || 'epic',
+    status: state.status || 'available',
+    owner: state.owner || null,
+    branch: state.branch || null,
+    validation: state.validation || 'pending',
+    review: state.review || 'not-requested',
+    project: state.project || { state: 'backlog', fields: {} },
+    dependencies: Array.isArray(state.dependencies) ? state.dependencies : [],
+    tasks: Array.isArray(state.tasks) ? state.tasks : [],
+    labels: Array.isArray(state.labels) ? state.labels : [],
+    lastAction: state.lastAction || 'sync',
+    lastActionAt: state.lastActionAt || new Date().toISOString(),
+    lastSyncAt: state.lastSyncAt || new Date().toISOString(),
+    notes: state.notes || null,
+  };
+
+  return [
+    `<!-- ${marker}:start -->`,
+    '```json',
+    JSON.stringify(payload, null, 2),
+    '```',
+    `<!-- ${marker}:end -->`,
+  ].join('\n');
+}
+
+function mergeIssueBody(issue, nextState, policy = DEFAULT_POLICY) {
+  const body = String(issue.body || '');
+  const markerEscaped = escapeRegExp(policy.sectionMarker || DEFAULT_SECTION_MARKER);
+  const rendered = renderCoordinationState(nextState, policy);
+  const regex = new RegExp(
+    `\\n?<!--\\s*${markerEscaped}:start\\s*-->[\\s\\S]*?<!--\\s*${markerEscaped}:end\\s*-->\\n?`,
+    'm'
+  );
+
+  if (regex.test(body)) {
+    return body.replace(regex, `\n${rendered}\n`).trim() + '\n';
+  }
+
+  const trimmed = body.trimEnd();
+  if (!trimmed) {
+    return `${rendered}\n`;
+  }
+
+  return `${trimmed}\n\n${rendered}\n`;
+}
+
+module.exports = {
+  escapeRegExp,
+  extractCoordinationState,
+  extractIssueReferences,
+  extractTasks,
+  mergeIssueBody,
+  normalizeBodyForComparison,
+  parseStringList,
+  renderCoordinationState,
+};