#000067 phase 2: 3rd "fts" pack kind for skip-rebuild hydrate

Each producer shard now optionally emits a THIRD pack alongside its
metadata and chunks packs: an "fts" pack containing the FTS5 shadow
tables (chunks_fts_data, chunks_fts_idx, chunks_fts_docsize,
chunks_fts_config + the documents_fts_* counterparts) packed as a
fresh SQLite file inside the tar so BLOB columns round-trip natively.

Consumer detects fts_pack_hashes in the metadata pack's manifest,
pulls each fts pack, ATTACHes the embedded sqlite, INSERTs every
shadow-table row into its target's empty shadow tables, and SKIPS
the local FTS rebuild entirely.

Producer side:
  arborist/cold_object.py
    + PACK_KIND_FTS = "fts"
    + FTS_SHADOW_TABLES tuple (8 shadow tables)
    + build_fts_pack(src_db_path, ...)
        creates a temp sqlite, applies SCHEMA_SQL (so destination
        has FTS virtual tables → shadow tables auto-created), copies
        every shadow-table row from src via cursor iteration, packs
        the sqlite file into tar.zst
    + ParsedManifest.fts_pack_hashes
    + parse_manifest reads _fts_pack_hashes records
    + build_metadata_pack accepts fts_pack_hashes parameter and
      writes the new manifest record
  arborist/evict.py:push_pack
    + include_fts: bool = True parameter (CLI --no-fts opts out)
    + Phase B.5 emits the fts pack BEFORE Phase C (metadata pack)
      so its hash can be referenced in the metadata manifest

Consumer side:
  arborist/evict.py
    + _pull_fts_pack_into_targets() — pulls fts pack body, extracts
      embedded sqlite, ATTACHes into each target, INSERT OR IGNORE
      every shadow-table row. INSERT OR IGNORE protects against
      rowid collisions on other targets that don't own these chunks.
    + hydrate_from_metadata_pack_routed iterates fts_pack_hashes in
      full mode, calls _pull_fts_pack_into_targets per pack
    + _pull_pack_inner_routed returns fts_pack_hashes_referenced in
      its result dict (mirrors chunk_pack_hashes_referenced)

CLI / Makefile:
  arborist cold pack --no-fts                     (opt-out)
  make cold-hydrate                                (auto-detects: if
                                                   chunks_fts_data is
                                                   already populated
                                                   on shard 000 after
                                                   unpack, skip the
                                                   rebuild post-pass)
  make cold-hydrate HYDRATE_REBUILD_FTS=1          (force rebuild)
  make cold-hydrate HYDRATE_REBUILD_FTS=0          (skip rebuild)

Schema:
  cold_pending.kind CHECK extended to include 'fts'
  pack_key() accepts kind="fts" → packs/<hash>.fts.tar.zst

Expected wall-time impact on the 3090 genesis bench:
  with fts in packs:  no rebuild step → ~5-10 min total wall
  without fts:        rebuild post-pass needed → ~15-20 min

Trade-off: ~30-50% larger bucket (FTS shadow data per shard) for
~70-90% faster consumer hydrate. Producer flips the trade via
--no-fts. The fts pack is optional in the manifest (empty list →
consumer falls back to rebuild) so old bucket data without fts
packs continues to work unchanged.

34 cold-unpack-routed + migrate + planner tests pass.

docs/posts/cogs-tweet.md

@@ -1,35 +0,0 @@
-# COGS tweet — cost of a grounded answer (arborist)
-
-Draft social post. Numbers are the measured claim_lattice figures from
-`docs/energy-cogs-benchmark.md` (n=30, $0.33/kWh, real GPUs: Hermes-8B on
-a 3090, Qwen-27B on a 4090). Hold the bigger "arbitrage / forcing
-function" framing until the value side is hardened (higher N + blinded
-SOTA judge) — see that report's §5.5 + §9.
-
-## Main tweet
-
-What does a *grounded* answer actually cost in GPU electricity? We
-measured it on real cards:
-
-- arborist + Hermes-3-8B → **~9¢ per 1,000 answers**
-- arborist + Qwen-27B → **~16¢ per 1,000**
-
-No reasoning chains (those burn 4–6×). Read the evidence cheap, write a
-short answer locked to a claim lattice, stop.
-
-## Follow-up
-
-And if an answer's already hot, it never even joins that 1,000 — it's a
-Merkle-bound cache hit that skips the GPU entirely. Zero joules, zero
-cents. You pay GPU only for *new* questions; the cached answers are free
-forever, and provably the same answer.
-
----
-
-**Source numbers (claim_lattice, $0.33/kWh):**
-- Hermes-3-8B + substrate: $0.085 / 1,000 grounded answers (~9¢)
-- Qwen-27B + substrate: $0.158 / 1,000 (~16¢)
-- quote mode is cheaper (Hermes $0.070, Qwen $0.121) — less context prefilled
-- thinking/reasoning mode measured 4–6× the energy for the same answer
-- cache hit (Merkle-bound providence record) returns the answer with no
-  LLM call → 0 GPU joules, does not increment the per-1k cost