fix(server): skip disabled settlement lookups

[t3dotgg]

Rebase of #10313 by @yashranaway onto current main. My token could not push the rebase to the fork, so this carries the same commit with the conflicts resolved.

Problem

ThreadSettlementReactor.sweep ran the full shell snapshot read and pull request lookup before checking whether auto-settlement is enabled. With sidebarAutoSettleOnMerge: false and sidebarAutoSettleAfterDays: null a server with many worktrees still spawned about 50 git processes a minute for work that could never settle a thread. Reported in #9714.

Fix

Read settings first in sweep and return when both auto-settle options are off. The new test covers startup, timer, and merge sweeps while disabled, and confirms work resumes when a setting turns on. Since #10103 inactive threads settle without a PR lookup, so the rebased test asserts on dispatched commands rather than lookup counts.

Closes #9714. Supersedes #10313.

Rebased and verified by Claude Fable 5.1 in Claude Code. Original change by @yashranaway.

[macroscopeapp]

Approvability

Verdict: Would Approve

Macroscope's review found this PR approvable — The PR adds an early exit that prevents snapshot and pull-request lookups when both existing auto-settlement options are disabled, while preserving enabled behavior. Focused tests cover startup, timer, merge, and re-enable scenarios, and no product defaults or static-analysis settings are changed.

Not approved because:

• Monthly spending limit reached (workspace setting). Approvability relies on correctness review in order to determine eligibility

^{Review your spending limits in Billing settings. You can add or adjust custom eligibility rules. Learn more.}

[github-actions]

Thread transfer impact

✅ Thread transfer remains within every enforced ceiling.

Provider	Metric	Main baseline	This PR	Impact	PR ceiling
Codex	Total thread wire	13.5 KiB	13.6 KiB	+60 B (+0.4%)	15.1 KiB	✅
Codex	Thread snapshot wire	7.0 KiB	7.0 KiB	+1 B (+0.0%)	7.3 KiB	✅
Codex	Live turn WebSocket wire	6.5 KiB	6.6 KiB	+59 B (+0.9%)	7.8 KiB	✅
Codex	Live turn WebSocket decoded	57.0 KiB	57.1 KiB	+88 B (+0.2%)	66.4 KiB	✅
Codex	Live turn messages	8	10	+2 (+25.0%)	21	✅
Claude	Total thread wire	13.6 KiB	13.6 KiB	+52 B (+0.4%)	15.1 KiB	✅
Claude	Thread snapshot wire	7.0 KiB	7.1 KiB	+7 B (+0.1%)	7.3 KiB	✅
Claude	Live turn WebSocket wire	6.5 KiB	6.6 KiB	+45 B (+0.7%)	7.8 KiB	✅
Claude	Live turn WebSocket decoded	57.8 KiB	57.9 KiB	+88 B (+0.1%)	66.4 KiB	✅
Claude	Live turn messages	8	10	+2 (+25.0%)	21	✅

Baseline: d6aa179 · PR result: 0a3ca8f · Source CI: success

Scenario and decoded snapshot size

10 historical turns, 5 command tools per turn, 878.9 KiB retained MCP result per historical turn, and a 1.05 MiB retained result in the measured turn.

• Codex decoded thread snapshot: 113.9 KiB
• Claude decoded thread snapshot: 114.6 KiB

Updated in place by a trusted workflow. PR artifacts are strictly validated and never executed.