G0 D3: catalogd Parquet manifests + ADR-020 idempotent register · 6 scrum fixes

Phase G0 Day 3 ships catalogd: Arrow Parquet manifest codec, in-memory
registry with the ADR-020 idempotency contract (same name+fingerprint
reuses dataset_id; different fingerprint → 409 Conflict), HTTP client
to storaged for persistence, and rehydration on startup. Acceptance
smoke 6/6 PASSES end-to-end including rehydrate-across-restart — the
load-bearing test that the catalog/storaged service split actually
preserves state.

dataset_id derivation diverges from Rust: UUIDv5(namespace, name)
instead of v4 surrogate. Same name on any box generates the same
dataset_id; rehydrate after disk loss converges to the same identity
rather than silently re-issuing. Namespace pinned at
a8f3c1d2-4e5b-5a6c-9d8e-7f0a1b2c3d4e — every dataset_id ever issued
depends on these bytes.

Cross-lineage scrum on shipped code:
  - Opus 4.7 (opencode):                       1 BLOCK + 5 WARN + 3 INFO
  - Kimi K2-0905 (openrouter, validated D2):   2 BLOCK + 2 WARN + 1 INFO
  - Qwen3-coder (openrouter):                  2 BLOCK + 2 WARN + 2 INFO

Fixed:
  C1 list-offsets BLOCK (3-way convergent) → ValueOffsets(0) + bounds
  C2 Rehydrate mutex held across I/O → swap-under-brief-lock pattern
  S1 split-brain on persist failure → candidate-then-swap
  S2 brittle string-match for 400 vs 500 → ErrEmptyName/ErrEmptyFingerprint sentinels
  S3 Get/List shallow-copy aliasing → cloneManifest deep copy
  S4 keep-alive socket leak on error paths → drainAndClose helper

Dismissed (false positives, all single-reviewer):
  Kimi BLOCK "Decode crashes on empty Parquet" — already handled
  Kimi INFO "safeKey double-escapes" — wrong, splitting before escape is required
  Qwen INFO "rb.NewRecord() error unchecked" — API returns no error

Deferred to G1+: name validation regex, per-call deadlines, Snappy
compression, list pagination continuation tokens (storaged caps at
10k with sentinel for now).

Build clean, vet clean, all tests pass, smoke 6/6 PASS after every
fix round. arrow-go/v18 + google/uuid added; Go 1.24 → 1.25 forced
by arrow-go's minimum.

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

lakehouse.toml

@@ -12,6 +12,7 @@ bind = "127.0.0.1:3211"
 
 [catalogd]
 bind = "127.0.0.1:3212"
+storaged_url = "http://127.0.0.1:3211"
 
 [ingestd]
 bind = "127.0.0.1:3213"