feat(voyage)!: rename stats filenames, settings keys, hook prefixes [skip-docs]

- lib/stats/event-emit.mjs: STATS_FILENAME -> trekexecute-stats.jsonl + comment
- hooks/scripts/post-bash-stats.mjs: stats target + comment -> trekexecute-stats.jsonl
- lib/stats/cache-analyzer.mjs: help-text + comment -> trekexecute-stats.jsonl
- tests/lib/stats-event-emit.test.mjs (lines 104, 117): fixture assertions
- settings.json: ultraplan/ultraresearch -> trekplan/trekresearch keys + statsFile values
- tests/lib/doc-consistency.test.mjs: allowlist (line 83) + accessor cfg.ultraplan?.* -> cfg.trekplan?.* (lines 91, 93) — atomic-pair, prevents vacuous undefined assertions
- scripts/q3-cache-prefix-experiment.mjs: STATS_JSONL hardcoded path -> voyage data dir + trekexecute filename
- hooks/scripts/pre-bash-executor.mjs (2 lines), pre-compact-flush.mjs (2 lines), pre-write-executor.mjs (1 line): [ultraplan]/[ultraplan-local] stderr prefix -> [voyage]
- commands + agents/review-orchestrator.md + CLAUDE.md: prose stats filename literals -> trek* equivalents

Atomic per session-spec: settings.json scope keys + doc-consistency.test.mjs
allowlist + property accessors committed together to prevent silent vacuous
undefined-equals-undefined assertions.

Part of voyage-rebrand session 2 (W3.7 / Step 9).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

plugins/ultraplan-local/tests/lib/stats-event-emit.test.mjs

@@ -101,7 +101,7 @@ test('emit never throws when stats path is unwritable', () => {
 
 test('resolveStatsPath honors CLAUDE_PLUGIN_DATA env var', () => {
   const r = resolveStatsPath({ CLAUDE_PLUGIN_DATA: '/var/data/plugin' });
-  assert.equal(r, '/var/data/plugin/ultraexecute-stats.jsonl');
+  assert.equal(r, '/var/data/plugin/trekexecute-stats.jsonl');
   assert.equal(resolveStatsPath({}), null);
 });
 
@@ -114,7 +114,7 @@ test('CLI shim writes via emit when CLAUDE_PLUGIN_DATA is set', () => {
       env: { ...process.env, CLAUDE_PLUGIN_DATA: dir },
       encoding: 'utf-8',
     });
-    const path = join(dir, 'ultraexecute-stats.jsonl');
+    const path = join(dir, 'trekexecute-stats.jsonl');
     assert.ok(existsSync(path));
     const line = readFileSync(path, 'utf-8').trim();
     const parsed = JSON.parse(line);