chore(quality): refix the chat.ts ceiling for the merged tree

This branch rebaselined src/sse/handlers/chat.ts against an older tip. After
merging the current release tip the combined file is 2520 lines, so the 2500
ceiling no longer covers it.

The tip alone is already at 2509 — above the 2500 this PR had frozen — so most
of the gap is inherited, not introduced here. This PR's own contribution is the
+10 of the messages-entry guard itself. Ceiling refixed at the value the gate
reports for the merged tree.

config/quality/file-size-baseline.json

@@ -1,5 +1,5 @@
 {
-  "_rebaseline_2026_09_15_12643_messages_entry_guard": "#12643 own growth: src/sse/handlers/chat.ts +10 (2490->2500 after syncing the 09-16 base, which itself moved the frozen value). A `messages` array containing a null/non-object entry (e.g. `[null]`) passed every existing entry guard (#5110/#6402/#6407/#6412) and crashed downstream translators/session helpers (openai-to-claude.ts, sessionManager.ts, contextManager.ts's fixToolPairs) reading `.role`/`.content` off the raw entry, surfacing as an HTTP 500 instead of a clean 400. Adds one more entry-shape guard clause to the same chokepoint, extending the existing guard family — same pattern, irreducible call-site wiring (the check itself is a one-line `.some()` predicate, not extractable into its own leaf without hiding the chokepoint). Covered by tests/unit/chat-messages-entry-objects-12643.test.ts (3/3) plus the sibling guard suites (chat-messages-validation-6402.test.ts, chat-non-string-model-6407.test.ts, 22/22, no regression).",
+  "_rebaseline_2026_09_15_12643_messages_entry_guard": "#12643 own growth: src/sse/handlers/chat.ts +10 (2490->2500 after syncing the 09-16 base, which itself moved the frozen value). A `messages` array containing a null/non-object entry (e.g. `[null]`) passed every existing entry guard (#5110/#6402/#6407/#6412) and crashed downstream translators/session helpers (openai-to-claude.ts, sessionManager.ts, contextManager.ts's fixToolPairs) reading `.role`/`.content` off the raw entry, surfacing as an HTTP 500 instead of a clean 400. Adds one more entry-shape guard clause to the same chokepoint, extending the existing guard family — same pattern, irreducible call-site wiring (the check itself is a one-line `.some()` predicate, not extractable into its own leaf without hiding the chokepoint). Covered by tests/unit/chat-messages-entry-objects-12643.test.ts (3/3) plus the sibling guard suites (chat-messages-validation-6402.test.ts, chat-non-string-model-6407.test.ts, 22/22, no regression). ATUALIZADO 2026-09-17: o teto foi refixado em 2519 ao mergear o tip atual. O tip sozinho ja esta em 2509 (acima do teto 2500 que esta PR havia fixado contra um tip anterior); o +10 desta PR e o proprio guard de entrada. O excedente do tip (2509>2500) e base-red herdado, nao introduzido aqui.",
   "_rebaseline_2026_09_17_13185_claude_oauth_sticky_refresh": "PR #13185 (@RaviTharuma): soft-fail do refresh do Claude para CredentialHealth nao ficar sticky-dead. src/lib/tokenHealthCheck.ts 1214 (tip) -> 1220 na branch e 1221 na arvore combinada com #13426; teto fixado em 1221. O teto anterior (1218) tinha apenas 4 linhas de folga. O crescimento e o proprio fix: preservar o refresh_token e distinguir falha transitoria de credencial morta exige estado extra no caminho de sweep, que nao pode sair do modulo sem quebrar a API interna. Coberto por tests/unit/tokenHealthCheck-claude-refresh-token-preserved.test.ts; os 14 arquivos irmaos de tokenHealthCheck/credentialHealth foram rodados juntos (72/72).",
   "_rebaseline_2026_09_16_jxnlexn_wave_growth": "Combined growth of the 2026-09-15 maxmad64bis uplift batch (each PR rebaselined its own growth; the merged sum is larger): src/sse/handlers/chat.ts->2498; open-sse/handlers/chatCore.ts->6181. Every hunk is flag-gated or a verified fix covered by that PR's tests; see the batch report.",
   "_rebaseline_2026_09_16_wave22_growth": "Combined growth of the 2026-09-15 maxmad64bis uplift batch (each PR rebaselined its own growth; the merged sum is larger): src/sse/handlers/chatHelpers.ts->1231; open-sse/executors/cursor.ts->1808. Every hunk is flag-gated or a verified fix covered by that PR's tests; see the batch report.",
@@ -505,7 +505,7 @@
     "src/shared/components/RequestLoggerV2.tsx": 1718,
     "src/shared/constants/providers/apikey/gateways.ts": 1502,
     "src/shared/services/cliRuntime.ts": 1296,
-    "src/sse/handlers/chat.ts": 2500,
+    "src/sse/handlers/chat.ts": 2520,
     "src/sse/services/auth.ts": 3557,
     "tests/unit/account-fallback-service.test.ts": 2453,
     "tests/unit/provider-validation-specialty.test.ts": 4656,