refactor(kiro): keep terminal integrity transport-only

[SemonCat]

Summary

• remove response-text heuristics from the Kiro transport integrity gate
• pass ellipses and future-action/progress prose through unchanged
• preserve EventStream validation, terminal provenance, bounded retry, and malformed nested tool_call repair

Why

PR #2717 added the right transport protections, but it also made the router infer task completeness from answer wording. The router has no user goal or tool history, so those language-specific guesses can retry valid output and encode caller policy in the provider adapter.

This follow-up keeps the boundary strict:

• 9Router: framing, CRC/header validation, terminal metadata, upstream errors, timeouts/cancellation, bounded protocol retry, malformed tool-call repair
• caller/agent: whether the requested task is semantically complete, blocked, or should continue

Scope

Only the Kiro executor and its terminal-integrity tests change. No credit, auth, affinity, Responses, GPT, cache, pricing, or plugin changes are included.

Verification

• Kiro-focused tests: 10 files, 161 passed, 2 expected failures
• terminal-integrity suite: 69/69 passed
• touched-file ESLint and Node syntax checks: passed
• production build: passed (130/130 static pages)
• git diff --check: passed
• independent Claude Code review: no accepted/actionable findings