fix(gemini-local): treat token-overflow as a fresh-session signal (#4932)

## Thinking Path

The same 2026-04-30 audit that produced PR #4118 (`Invalid session`
regex extension) and the ENOTFOUND classifier (#4931) identified a third
stuck-session pattern: **13 failures in 7 days, all on a single agent
(Ernest)**, with stderr matching:

```
_ApiError: {"error":{"code":400,"message":"The input token count exceeds
the maximum number of tokens allowed 1048576","status":"INVALID_ARGUMENT"}}
  at ChatCompressionService.compress
```

The root cause is that gemini-cli's `ChatCompressionService` blew the 1M
token context limit **during its compression step itself**. Resuming the
same session ID will hit the same wall on the next attempt — the session
is effectively dead the same way it is when "Invalid session identifier"
fires (PR #4118).

## What Changed

Extends the `isGeminiUnknownSessionError` regex in `parse.ts` with two
phrases:
- `exceeds\s+the\s+maximum\s+number\s+of\s+tokens`
- `input\s+token\s+count\s+exceeds`

Both trigger the **existing** fresh-session retry path in
`execute.ts:596` — no new code path. Same extension pattern as PR #4118.

## Verification

- `npx vitest run --project @paperclipai/adapter-gemini-local` → 14/14
pass (11 in `parse.test.ts` + 3 existing in `execute.remote.test.ts`)
- 2 new tests cover the token-overflow patterns
- `pnpm --filter @paperclipai/adapter-gemini-local typecheck` → clean
- Audit query against `heartbeat_runs.stderr_excerpt` confirms regex
matches all 13 occurrences

## Stacking

This PR is stacked on top of #4931 (the ENOTFOUND classifier) which adds
the `parse.test.ts` file. If #4931 merges first, this PR's diff is just
the regex + 2 tests. If this PR is reviewed first, please merge #4931
first to avoid touching the same test scaffolding twice.

## Risks

- **Low.** Single-line regex extension. No new code paths.
- The session-reset path is well-trodden (PR #4118 in flight).
- If a non-Gemini caller produces a stderr containing "exceeds the
maximum number of tokens" by coincidence, they would trigger one
unnecessary fresh-session retry. Not plausible in the gemini-cli output
context where this stderr is sourced.

## Model Used

Claude Opus 4.7 (1M context), Anthropic SDK via Claude Code CLI.

## Checklist

- [x] Thinking path traces from audit data to single-line regex change
- [x] Model specified
- [x] No duplicate of planned core work
- [x] Tests pass locally
- [x] Tests added (2 new)
- [x] N/A — server-side regex
- [x] Internal pattern; no docs change
- [x] Risks documented
- [x] Will address Greptile + reviewer comments before merge
- [x] I searched the GitHub PR list for similar PRs and confirmed this
is not a duplicate (related: #4118 covers the "Invalid session
identifier" regex; this PR extends the same regex with token-overflow
phrases)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: Devin Foley <devin@paperclip.ing>
Co-authored-by: Paperclip <noreply@paperclip.ing>

server/src/__tests__/adapter-session-codecs.test.ts

@@ -7,7 +7,7 @@ import {
 } from "@paperclipai/adapter-cursor-local/server";
 import {
   sessionCodec as geminiSessionCodec,
-  isGeminiUnknownSessionError,
+  isGeminiSessionUnrecoverableError,
 } from "@paperclipai/adapter-gemini-local/server";
 import {
   sessionCodec as opencodeSessionCodec,
@@ -220,19 +220,19 @@ describe("cursor resume recovery detection", () => {
 describe("gemini resume recovery detection", () => {
   it("detects unknown session errors from gemini output", () => {
     expect(
-      isGeminiUnknownSessionError(
+      isGeminiSessionUnrecoverableError(
         "",
         "unknown session id abc",
       ),
     ).toBe(true);
     expect(
-      isGeminiUnknownSessionError(
+      isGeminiSessionUnrecoverableError(
         "",
         "checkpoint latest not found",
       ),
     ).toBe(true);
     expect(
-      isGeminiUnknownSessionError(
+      isGeminiSessionUnrecoverableError(
         "{\"type\":\"result\",\"subtype\":\"success\"}",
         "",
       ),

server/src/__tests__/gemini-local-adapter.test.ts

@@ -1,7 +1,7 @@
 import { describe, expect, it, vi } from "vitest";
 import {
   isGeminiTurnLimitResult,
-  isGeminiUnknownSessionError,
+  isGeminiSessionUnrecoverableError,
   parseGeminiJsonl,
 } from "@paperclipai/adapter-gemini-local/server";
 import { parseGeminiStdoutLine } from "@paperclipai/adapter-gemini-local/ui";
@@ -76,8 +76,8 @@ describe("gemini_local parser", () => {
 
 describe("gemini_local stale session detection", () => {
   it("treats missing session messages as an unknown session error", () => {
-    expect(isGeminiUnknownSessionError("", "unknown session id abc")).toBe(true);
-    expect(isGeminiUnknownSessionError("", "checkpoint latest not found")).toBe(true);
+    expect(isGeminiSessionUnrecoverableError("", "unknown session id abc")).toBe(true);
+    expect(isGeminiSessionUnrecoverableError("", "checkpoint latest not found")).toBe(true);
   });
 });