fix(runtime): restore session ID after compaction and drop forced overflow compaction

[hetaoBackend]

Summary

Follow-up to #459 and #460.

• Drop the forced compaction after oversized requests. fix: stop retrying oversized requests and recover with one forced compaction #460 added a one-shot compact-and-resend after a provider rejected a main-agent request as too large. The resend skipped the normal before-LLM pipeline, so request-level transforms were not reapplied to it: the computer-use screenshot cap, and the session identity restoration below. This removes contextOverflowRecoveryHook, the force: 'context_overflow_recovery' compaction input, and the forced compaction limits. Oversized requests (HTTP 413, request_too_large, the local request-body check, context-window overflow) are still classified as deterministic rejections and are not resent unchanged. isLLMRequestOversized becomes module-private, and its cases are asserted through isLLMDeterministicRequestRejection.
• Restore the session ID after compaction drops it. perf(runtime): trim per-turn reminders (budget thresholds, minute time, session id once) #459 omits YOUR SESSION ID from the turn reminder while earlier history already shows it. If automatic compaction (including the initial compaction of the same turn) summarizes that history away, the model lost its session ID until the next turn. A stateless post-compaction hook now appends a hidden session_identity_reminder when no visible user message or identity reminder after the latest compaction carries the ID. On initial compaction it goes before the current user message; mid-turn it goes at the tail. The preparation check counts this reminder too, so the next turn does not repeat the ID.

Verification

• pnpm typecheck, pnpm build, pnpm check:standalone, pnpm check:source, pnpm check:tsconfig, pnpm test:release-tools, pnpm lint:tui all pass.
• pnpm test:capabilities: 217 files, 5421 passed, 17 skipped. pnpm test:policy: 142 passed.
• Focused: the new session-identity-reminder.test.ts, plus llm-retry, automatic-context-compactor, executor, context-compaction (296 passed).

Not verified: real-model behaviour after compaction, and Windows.

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