v1.12.4: complete inference.ts split into services/inference/

- sentinel-summaries.ts: runCapHitSummary, insertCapHitSentinel,
  runDoomLoopSummary, insertDoomLoopSentinel
- inference.ts → inference/turn.ts: residue is runAssistantTurn,
  runInference, createInferenceRunner orchestration only
- inference/index.ts: re-export shim preserves the public surface
  (createInferenceRunner, runInference, runAssistantTurn,
  detectDoomLoop, DOOM_LOOP_THRESHOLD, buildMessagesPayload, plus
  type-side InferenceContext/InferenceFrame/StreamResult/TurnArgs/
  FramePublisher)
- src/index.ts + auto_name.ts + the two vitest test files updated to
  import from ./services/inference/index.js explicitly (NodeNext ESM
  doesn't honor directory-index resolution)

Final tally: 11 files under services/inference/, the largest being
sentinel-summaries.ts at 523 LoC (two near-clone summary paths kept
side-by-side until a third sentinel justifies factoring out a shared
runWrapUpSummary). turn.ts is now 326 LoC, the next-largest is
stream-phase.ts at 380. Public import surface unchanged.

tool-phase.ts → turn.ts back-edge for runAssistantTurn remains
(cycle is safe; resolved at call time).

Prepares the file structure for v1.13 AI SDK migration — streamText
swap targets stream-phase.ts only.

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

apps/server/src/services/inference/tool-phase.ts

@@ -7,12 +7,12 @@ import type {
   InferenceContext,
   StreamResult,
   TurnArgs,
-} from '../inference.js';
+} from './turn.js';
 // v1.12.4: ESM value-import cycle. executeToolPhase recurses into
 // runAssistantTurn which lives in inference.ts. The cycle is safe because
 // the reference is read at call time (inside an async function body), not
 // at module top-level. Node + tsc resolve this cleanly.
-import { runAssistantTurn } from '../inference.js';
+import { runAssistantTurn } from './turn.js';
 
 async function executeToolCall(
   projectRoot: string,