auditor: 3 fixes from Opus self-audit on 454da15 + tree-split deletion

The post-fix audit on commit 454da15 produced a fresh BLOCK and
re-flagged the dead tree-split as still dead. This commit lands the
BLOCK fix and the deletion.

LANDED:

1. kimi_architect.ts:113 BLOCK — MAX_TOKENS=128_000 exceeds Anthropic
   Opus 4.x's 32K output cap. Worked silently (Anthropic clamps
   server-side) but was technically invalid. Replaced single-default
   with `maxTokensFor(model)` returning per-model caps:
     claude-opus-*    -> 32_000  (Opus extended-output)
     claude-haiku-*   -> 8_192   (Haiku/Sonnet default)
     claude-sonnet-*  -> 8_192
     kimi-*           -> 128_000 (reasoning_content needs headroom)
     gpt-5*/o-series  -> 32_000
     default          -> 16_000  (conservative)
   LH_AUDITOR_KIMI_MAX_TOKENS env override still works (forces value
   regardless of model).

2. inference.ts dead-code removal — Opus flagged tree-split as still
   dead post-2026-04-27 mode-runner rebuild. Removed 156 lines:
     runCloudInference   (lines 464-503)  legacy /v1/chat caller
     treeSplitDiff       (lines 547-619)  shard-and-summarize fn
     callCloud           (lines 621-651)  helper for treeSplitDiff
     SHARD_MODEL         const            qwen3-coder:480b
     SHARD_CONCURRENCY   const            6
     DIFF_SHARD_SIZE     const            4500
     CURATION_THRESHOLD  const            30000
   No live callers — verified by grep before deletion. The mode
   runner's matrix retrieval against lakehouse_answers_v1 supplies
   the cross-PR context that tree-split was synthesizing from scratch.

3. inference.ts:38-49 stale comment about "curate via tree-split"
   replaced with current "matrix retrieval supplies cross-PR context"
   semantics. Block was already physically gone but the comment
   describing it remained, contradicting the actual code path.

SKIPPED (defensible / minor):

- WARN: outage sentinel TTL refresh on continued failure — intentional
  (refresh keeps cache valid while upstream is still down)
- WARN: enrichment counts use Math.max — defensible (consensus
  enrichment IS the max of the three runs)
- WARN: parseFindings regex eats severity into rationale on multi-
  paragraph inputs — minor, hasn't affected grounding rate
- WARN: selectModel uses pre-truncation diff.length — defensible
  (promotion is "is this audit worth Opus", not "what does the model
  see")
- INFO×3: static.ts state reset, parentStruct walk bound,
  appendMetrics 0-finding rows — all defensible per current intent

Verification:
  bun build auditor/checks/{inference,kimi_architect}.ts   compiles
  systemctl restart lakehouse-auditor.service              active

Net: -184 lines, +29 lines (155 net deletion).

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

auditor/checks/kimi_architect.ts

@@ -69,18 +69,28 @@ function selectModel(diffLen: number): { provider: string; model: string; promot
   }
   return { provider: KIMI_PROVIDER, model: KIMI_MODEL, promoted: false };
 }
-// 128K — Kimi K2.6 emits reasoning_content that counts against this
-// budget but isn't surfaced in the OpenAI-shape `content` field.
-// Capping low silently produces empty content with finish_reason=length
-// when reasoning consumes the budget. 128K leaves ample room for both
-// reasoning and visible findings on any audit prompt we throw at it.
-// Override via LH_AUDITOR_KIMI_MAX_TOKENS only if you want to cap cost.
+// Model-aware max_tokens. Different upstream APIs cap at different
+// limits and reject requests that exceed them:
+//   - Anthropic Opus 4.x: 32K output (with extended-output header)
+//   - Anthropic Haiku 4.5: 8K output
+//   - Kimi K2.6 (reasoning): 128K — needs headroom because
+//     reasoning_content counts against the budget
+//   - Default: 16K, conservative middle ground
 //
-// Bug fix 2026-04-27 (caught by Kimi's own self-audit): empty env var
-// like LH_AUDITOR_KIMI_MAX_TOKENS="" used to parse via Number("") → 0
-// because `??` only catches null/undefined. Use `||` so empty string,
-// 0, or NaN all fall back to the default.
-const MAX_TOKENS = Number(process.env.LH_AUDITOR_KIMI_MAX_TOKENS) || 128_000;
+// 2026-04-27 BLOCK from Opus self-audit: the prior single-default of
+// 128K worked silently (Anthropic clamps server-side) but was
+// technically invalid. Per-model caps make it explicit. Override via
+// LH_AUDITOR_KIMI_MAX_TOKENS to force a value (also fixes the empty-
+// env Number("") -> 0 trap by using `||` not `??`).
+const MAX_TOKENS_OVERRIDE = Number(process.env.LH_AUDITOR_KIMI_MAX_TOKENS) || 0;
+function maxTokensFor(model: string): number {
+  if (MAX_TOKENS_OVERRIDE > 0) return MAX_TOKENS_OVERRIDE;
+  if (model.startsWith("claude-opus")) return 32_000;
+  if (model.startsWith("claude-haiku") || model.startsWith("claude-sonnet")) return 8_192;
+  if (model.startsWith("kimi-")) return 128_000;
+  if (model.startsWith("gpt-5") || model.startsWith("o1") || model.startsWith("o3") || model.startsWith("o4")) return 32_000;
+  return 16_000;
+}
 
 export interface KimiArchitectContext {
   pr_number: number;
@@ -240,7 +250,7 @@ async function callKimi(prompt: string, provider: string, model: string): Promis
     provider,
     model,
     messages: [{ role: "user", content: prompt }],
-    max_tokens: MAX_TOKENS,
+    max_tokens: maxTokensFor(model),
     temperature: 0.2,
   });
   // curl via Bun.spawn — bypasses Bun fetch's ~300s intrinsic ceiling.