fix(cluster-tool): decode each outbound-gate code by its own carrier

[heifner]

The remaining chain-table reader flagged as [P1] on wire-sysio#619: "one live consumer bypasses it: ExternalOutpostSteps.ts still maps each getChains() row with String(code.value)."

Confirmed exactly as described. runOutboundEnvelopesQueued built its expected set with String(code.value) and compared spellings against String(row.chain_code). That worked only because both sides happened to land on the same decimal. Once the depot registers the slug_name ABI builtin, chains.code is "ETH", .value is undefined, every expected code becomes the literal "undefined", and the gate can never match — external-outpost bootstrap polls its full SingleHopBudgetMs and times out.

#101 did not expose it for two reasons: the reader bypasses slugValue entirely, so classifying slugValue call sites could not find it — and its fixture pinned { code: { value } }, so no test ever supplied the string carrier.

The fix

Both sides decode by declared type and compare packed values:

• chains.code is a slug_name ABI field → slugValue, which handles the {value} wrapper before the builtin and the canonical spelling after.
• outenvelopes.chain_code is declared uint64 → packedSlugValue, the decoder added in fix(cluster-tool): parse a bare slug cell as a slug, not a decimal #101 for precisely this carrier. It renders as a number, or a quoted decimal past 0xffffffff, which every real chain code exceeds.

The failure message keeps the human-readable form via SlugName.toString, so the enrichment context still names ETH / SOL rather than packed integers.

Fixture

chainRow is now parameterized over a SlugCarrier identity enum, and the gate's positive case runs under both carriers via it.each — the string spelling and the legacy {value} wrapper — so the rollout window is covered from both sides. Codes are real (ETH / SOL / WIRE) rather than small integers, so the spelling carrier is genuinely exercised.

I deliberately did not add a negative carrier case: the gate polls SingleHopBudgetMs (7 min) before failing, so a no-envelope test would stall the unit suite. The failure path is already covered by the existing enrichment test, which rejects through the fast getOutboundEnvelopes throw.

Verification

ExternalOutpostSteps + slugUtils: 30/30, 4.6s. Filtering to -t carrier gives 2 passed / 11 skipped, confirming both parameterized variants execute rather than silently collapsing to one. eslint clean on both files.

Order-independent, like #101: correct before and after #619.