fix(conversations): resolve turn content OmniRoute never sends back to the client

[hartmark]

What Problem This Solves

/dashboard/conversations's turn tree showed many turns as "Tool (empty)"/"Assistant (empty)" for genuine-continuation conversations, even though the actual content clearly existed and was served correctly.

Why This Change Was Made

resolveTurnDisplayContent only ever read a turn node's originating clientRawRequest.body — fine for a full-history-resend conversation (every later request's body eventually contains everything), but a genuine-continuation turn's own request only ever carries the NEW delta. That silently left the model's own generated tool_use/text turns unresolved — their content never appears in any request body, only in a response.

Verified against a real 133-node continuation conversation: request-only resolution left 131/133 nodes unresolved.

Added two more sources, read from the SAME already-loaded artifact (no extra I/O):

• the call's own clientResponse.output (the model's own generated turn — 131 → 76 unresolved)
• the call's own providerRequest.body (the server-reconstructed full history actually forwarded upstream for non-Responses-native providers, Chat Completions messages shape) — best-effort, translated text can differ byte-for-byte from what was originally hashed, so this doesn't close 100%, but it does close the "Tool (empty)" case entirely (76 → 21, all 112 tool nodes resolved; the remaining 21 are plain user/assistant text turns old enough to predate both available artifacts — genuinely lost history, not a resolution gap).

User Impact

The conversation tree now renders real content for tool calls and assistant turns in continuation-mode conversations instead of empty placeholders.

Evidence

Verified against a real production conversation (133 turn nodes): before/after unresolved-node counts (131 → 76 → 21) computed by replaying the exact resolution logic against the real stored artifacts.

🤖 Generated with Claude Code

[diegosouzapw]

sweep-reds / babysit: No new ESLint warnings is inherited from base-red #12581 — CodeQL ratchet 12 open > baseline 11 (repo-wide Security alerts, not this diff). No unused/@eloqnt findings here, so no ESLint code change.

Own FQG (complexity + open-sse typecheck TS2345) and API Route Typecheck are fixed in bae2cab01f by splitting conversationTurnContent.ts helpers and typing turns as the canonical role union. Did not merge origin/release/v3.8.51.

[diegosouzapw]

sweep-reds round 6 / babysit: remaining FQG after the typecheck/complexity split bae2cab01f is inherited from base-red #12581 — not this turn-content diff. Did not merge origin/release/v3.8.51.

• file-size: src/sse/handlers/chat.ts: 2434 > congelado 2424 — this PR does not touch chat.ts (one file: conversationTurnContent.ts).
• complexity-ratchets: CI merge-base 7802f6ea reported 118 changed files; local three-dot is 1. Listed regressions (attemptLogging.ts, tlsClientBase.ts, tlsClient.ts) are not this PR's file.

STOP on inherited FQG. Own split already landed.