… + autopilot purge) (#600)

* feat(v0.26.5): destructive operation guard — impact preview, confirmation gate, soft-delete

Three-layer protection against accidental data loss:

1. **Impact preview**: Every destructive operation (sources remove, purge)
   now shows a formatted preview of exactly what will be destroyed —
   page count, chunk count, embedding count, file count — BEFORE acting.

2. **--confirm-destructive flag**: `--yes` alone is no longer sufficient
   when a source has data. Must pass `--confirm-destructive` to proceed
   with permanent deletion. Prevents scripted/reflexive destroys.

3. **Soft-delete with 72h TTL**: New `gbrain sources archive <id>`
   hides a source from search and federation without destroying any data.
   Data preserved for 72 hours. Restorable via `gbrain sources restore <id>`.
   Expired archives purged via `gbrain sources purge`.

New subcommands:
  - `gbrain sources archive <id>` — soft-delete (hide, preserve 72h)
  - `gbrain sources restore <id>` — un-archive, re-federate
  - `gbrain sources archived` — list soft-deleted sources + TTL
  - `gbrain sources purge [<id>] [--confirm-destructive]` — permanent delete

Behavioral changes:
  - `sources remove` with data now requires `--confirm-destructive` (not just `--yes`)
  - `sources remove --dry-run` shows full impact preview without side effects
  - Impact box format shows source name, id, and all cascade counts

New files:
  - src/core/destructive-guard.ts — impact assessment, confirmation gate,
    soft-delete/restore/purge logic, display formatters

* chore(release): v0.26.5 — destructive operation guard

Bump VERSION + package.json to 0.26.5 and add the v0.26.5 CHANGELOG entry
on top of the destructive-guard feature commit cherry-picked from PR #595.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* feat(v0.26.5): page-level soft-delete + autopilot purge + search visibility

Closes the destructive-guard posture across every gbrain destructive surface.
PR #595 cherry-pick covered the CLI source-remove path; this commit closes
the higher-velocity MCP `delete_page` agent footgun and the three internal
correctness gaps the CEO+Eng review surfaced:

- Gap 1: archived sources were not actually filtered from search. Now they
  are, via `buildVisibilityClause` in `searchKeyword`/`searchKeywordChunks`/
  `searchVector` for both engines.
- Gap 2: 72h TTL was honor-system. Now wired into a new autopilot `purge`
  phase (9th in ALL_PHASES) that calls `purgeExpiredSources` + `engine.
  purgeDeletedPages(72)`. Manual escape hatch: `gbrain pages purge-deleted`.
- Gap 3: zero tests for safety-critical code. ~30 cases now in
  `test/destructive-guard.test.ts`, `test/pages-soft-delete.test.ts`, and
  `test/sql-ranking.test.ts` covering the boundary truth table, JSONB→column
  migration, soft-delete/restore/purge round-trip, multi-source isolation,
  cascade verification, and the Q3 IRON-rule contract test.

Schema migration v33 (`destructive_guard_columns`): adds `pages.deleted_at`
+ partial purge index, promotes `archived` from `sources.config` JSONB to
real columns (`sources.archived BOOLEAN`, `archived_at`, `archive_expires_at`),
backfills any pre-v0.26.5 JSONB shape. Engine-aware: Postgres uses CREATE
INDEX CONCURRENTLY, PGLite uses plain CREATE INDEX. Forward-reference
bootstrap extended in both engines so pre-v0.26.5 brains don't crash on the
embedded-schema replay.

BrainEngine surface: new `softDeletePage` / `restorePage` /
`purgeDeletedPages` methods + `includeDeleted` flag on `getPage`/`listPages`.
MCP ops: `delete_page` rewired to soft-delete (description string updated);
new `restore_page` (scope: write) + `purge_deleted_pages` (scope: admin,
localOnly: true).

Q3 contract (eng-review lynchpin): `get_page(slug)` returns null for
soft-deleted by default; `get_page(slug, {include_deleted: true})` surfaces
the row with `deleted_at` populated. Same flag for `list_pages`. Mirrors
the search-filter contract end-to-end.

Issue 5 (eng-review): `archived` is now a real column on `sources`, not a
JSONB key. No reserved-key footgun. Faster filter. Visibility clause
compiles to a column lookup, not JSONB containment.

Verification:
- bun run typecheck: PASS
- bun run build:schema + bun run build:llms: regenerated
- targeted test runs: 90 pass / 0 fail across destructive-guard,
  pages-soft-delete, sql-ranking, schema-bootstrap-coverage, build-llms
- full bun test: 16 pre-existing failures inherited from v0.26.2 (sync,
  sync-parallel, queue-child-done, etc — already filed in TODOS.md as
  "Fix 22 pre-existing test failures unrelated to OAuth")

CHANGELOG, CLAUDE.md (Key Files + Commands), TODOS.md updated. The plan
file at ~/.claude/plans/take-a-look-and-gentle-pine.md captures the full
review trail (CEO=C, Eng-Q3=A, Eng-Issue5=a, 8 defaults applied).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* fix(v0.26.5): CI fallout — getStats excludes soft-deleted; tests use --confirm-destructive

Two CI failures from the v0.26.5 ship:

1. **Tier 1 (Postgres E2E):** `E2E: Page CRUD > delete_page removes page and
   others survive` failed because `delete_page` now soft-deletes (sets
   deleted_at) but `getStats.page_count` was still counting all rows. The
   test seeds 16 pages, deletes one, and asserts page_count is 15. Fix:
   `getStats` now filters `WHERE deleted_at IS NULL` for page_count in both
   engines. This matches the visibility-filter contract — soft-deleted pages
   are hidden everywhere the user looks (search, get_page, list_pages, stats).
   Chunks and links stay raw because they still occupy storage until the
   autopilot purge phase runs.

2. **Test 2 (PGLite unit):** `multi-source-integration.test.ts:184` and
   `e2e/multi-source.test.ts:274` called `runSources(engine, ['remove', X,
   '--yes'])` against populated sources. v0.26.5's destructive guard rejects
   `--yes` alone on populated sources and calls `process.exit(5)`, which
   killed the bun test runner mid-suite (CI exit 5). Both test sites now
   pass `--confirm-destructive` per the v0.26.5 contract.

Verification: 115/0 pass across destructive-guard, pages-soft-delete,
sql-ranking, schema-bootstrap-coverage, sources, repos-alias, and
multi-source-integration test files. typecheck PASS.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* fix(test): cycle phase count is 9 (v0.26.5 added `purge` phase)

CI failure: `runCycle — yieldBetweenPhases hook` tests asserted exactly 8
phases. v0.26.5 added the autopilot `purge` phase as the 9th, so:

- `test/core/cycle.test.ts:381` — `hookCalls` is now 9 (one yield per phase)
- `test/core/cycle.test.ts:392` — `report.phases.length` is now 9
- `test/e2e/cycle.test.ts:101` — same update for the dry-run E2E

The `purge` phase invocation was already visible in the failing log output:
the cycle ran 9 phases end-to-end; the test assertions hadn't been updated.

Verification: bun run typecheck PASS. cycle.test.ts: 28/0 pass.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: garrytan-agents <garrytan-agents@users.noreply.github.com>
Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>