v0.42.13.0 fix(search): archive/ content findable by default, demoted not hard-excluded (#1777) (#1797)

* fix(search): archive/ findable by default — demote not hard-exclude (#1777)

Move archive/ out of DEFAULT_HARD_EXCLUDES into a 0.5 source-boost demote so
archived historical content is findable by default, ranked below curated
content. Add a hidden_by_search_policy doctor check so the surviving exclude
policy (test/, attachments/, .raw/) is auditable. Bump KNOBS_HASH_VERSION 8->9
so the policy change invalidates archive-excluded query_cache rows.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* chore: bump version and changelog (v0.42.13.0)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* docs: correct search-exclude.test.ts annotation for archive demote (#1777)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/core/postgres-engine.ts

@@ -1486,8 +1486,9 @@ export class PostgresEngine implements BrainEngine {
     // by multiplying the chunk-grain ts_rank with a source-factor CASE.
     // Detail-gated — disabled for `detail='high'` (temporal queries) so
     // chat surfaces normally for date-framed lookups. Hard-exclude prefixes
-    // (test/, archive/, attachments/, .raw/ by default) filter at the
-    // chunk-rank stage so they never enter the candidate set.
+    // (test/, attachments/, .raw/ by default) filter at the chunk-rank stage
+    // so they never enter the candidate set. (archive/ is demoted, not
+    // excluded — issue #1777.)
     const boostMap = resolveBoostMap();
     const sourceFactorCase = buildSourceFactorCase('p.slug', boostMap, opts?.detail);
     const hardExcludePrefixes = resolveHardExcludes(opts?.exclude_slug_prefixes, opts?.include_slug_prefixes);