feat(knowledge): model + effort routing enter the register, dated [skip-docs]

C1: two entries the optimization lens can cite for the model/effort axis,
both read out of the primary sources in this session rather than from the
plan's 2026-07-14 summary of them.

Verifying corrected the plan's own numbers: effort is settable in SIX
places, not five (/effort, the /model slider, --effort,
CLAUDE_CODE_EFFORT_LEVEL, settings effortLevel, skill/subagent
frontmatter), the default is high on every supporting model EXCEPT Opus
4.7 (xhigh), and the level count is model-dependent (Opus 4.6 and Sonnet
4.6 have no xhigh).

- BP-MODEL-001: subagent `model` defaults to `inherit`, so a subagent
  that names no model costs what the session costs; the documented pin
  is overridable by CLAUDE_CODE_SUBAGENT_MODEL and per-invocation model
- BP-MODEL-002: effort is an axis separate from model choice, and higher
  is not universally better (`max` "may show diminishing returns and is
  prone to overthinking")
- both carry the 2026-07-07 model/effort blog as a corroborating source
  with a real `published` date, so B1's evidence-age rule has teeth:
  measured stale with reasons ['evidence-age'] at a reference date 378
  days past publication while their verified stamps are pristine. The
  docs pages themselves get NO published date — they carry none, and
  guessing one in the field whose whole job is dating evidence is the
  lie the rule exists to catch
- new blanket guard: every corroborating source must carry a parseable
  published date. Without it newestEvidenceMs() returns null and the
  entry stays green on evidence of any age — a silent hole. Seen red
  against its own defect before it was trusted
- knowledge-refresh-cli's stale branch no longer expires on every new
  entry: its reference date has to sit after every `verified` stamp, was
  bumped once for BP-SUB-001 and would have needed a third bump now, so
  it moves to a date no stamp can reach

Register 14 -> 16 entries. Frozen v5.0.0 snapshots untouched (no scanner
output changes); suite 1579/0.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NKjojcdYYiCQP5AudUyQ5e

tests/scanners/knowledge-refresh-cli.test.mjs

@@ -9,19 +9,24 @@ import { tmpdir } from 'node:os';
 const __dirname = fileURLToPath(new URL('.', import.meta.url));
 const CLI = resolve(__dirname, '../../scanners/knowledge-refresh-cli.mjs');
 
-// The reference date must sit AFTER the newest entry's `verified` date, so every
-// entry is at least one day old and both the fresh and stale branches are
-// reachable deterministically, regardless of the real clock.
+// A fixed reference date keeps both branches reachable regardless of the real clock.
 //
-// It used to be 2026-06-21, on the premise that every seed entry was verified
-// 2026-06-20. That premise expired when BP-SUB-001 was added with a genuine
-// 2026-07-31 verification date — an entry verified *after* the reference date has
-// a negative age and counts as fresh, so `--stale-after 0` no longer emptied the
-// fresh bucket. Backdating the entry to fit the test would have been a lie about
-// when its source was checked; moving the reference date is the honest fix.
-// Bump this again when a newer entry lands.
+// REF is used by the fresh branch only, and needs no maintenance: an entry verified
+// after it has a negative age and still counts as fresh.
 const REF = '2026-08-01';
 
+// The stale branch needs a date strictly after EVERY entry's `verified` stamp — with
+// `--stale-after 0` an entry verified later than the reference date has a negative age,
+// lands in the fresh bucket, and empties nothing.
+//
+// This was REF itself, bumped 2026-06-21 → 2026-08-01 when BP-SUB-001 landed with a
+// genuine 2026-07-31 stamp, and it expired a second time when BP-MODEL-001/002 landed
+// verified 2026-08-10. Backdating an entry to fit the test would lie about when its
+// source was read, and re-deriving the date from the register would just assert the
+// register against itself. A date no verification stamp can reach satisfies the
+// requirement by construction, so no future entry expires it.
+const REF_AFTER_EVERY_STAMP = '2999-01-01';
+
 function runCli(extraArgs) {
   try {
     const stdout = execFileSync('node', [CLI, ...extraArgs], { encoding: 'utf-8', timeout: 15000 });
@@ -41,7 +46,10 @@ describe('knowledge-refresh-cli — exit codes', () => {
 
   it('exits 1 (advisory) when one or more entries are stale', () => {
     // stale-after 0 → anything verified before the reference date is stale.
-    const { status, stdout } = runCli(['--reference-date', REF, '--stale-after', '0']);
+    const { status, stdout } = runCli([
+      '--reference-date', REF_AFTER_EVERY_STAMP,
+      '--stale-after', '0',
+    ]);
     assert.equal(status, 1);
     const out = JSON.parse(stdout);
     assert.ok(out.counts.stale > 0);