feat(effort): add effort_lock setting to allow Claude Code /effort in-chat

[ckumar1]

Summary

Today gt always sets CLAUDE_CODE_EFFORT_LEVEL in the agent's environment, which causes Claude Code to lock the effort tier for the session and refuse the in-chat /effort command. Some operators want to seed the role default but still let the agent change tier mid-session via /effort. This PR makes the lock optional via a new effort_lock setting.

Motivation

The current behavior is appropriate for tightly-managed fleets where operators want strict per-role effort and don't want agents bumping themselves to higher tiers ad-hoc. But for solo operators and exploratory work, Claude Code's /effort is a natural in-chat knob, and the env-var lock surfaces as a confusing error: "Not applied: CLAUDE_CODE_EFFORT_LEVEL=high overrides effort this session". Today the only escape hatches are gt start --effort or GT_EFFORT, both of which require restarting the session.

Changes

• internal/config/types.go: add EffortLock *bool to both TownSettings and RigSettings. Pointer for tri-state (nil = use default).
• internal/config/loader.go: add ResolveEffortLock(townRoot, rigPath) bool — rig overrides town, defaults to true so existing fleets see no behavior change.
• internal/config/env.go: gate the env["CLAUDE_CODE_EFFORT_LEVEL"] = effort write on ResolveEffortLock returning true.
• internal/config/env_test.go: tests for effort_lock=false (env var omitted) and unset (defaults to locked).

Behavior

effort_lock	Env var written?	/effort in-chat
(unset) — default	yes	refused (current behavior)
true	yes	refused
false	no	works; Claude Code starts at its own default tier

When effort_lock=false, the role-resolved effort isn't applied at startup. Operators who want both — start at the role default AND allow /effort — would need a follow-up that passes effort via Claude Code's --effort CLI flag instead of via env var (potentially overridable by /effort); that's deliberately out of scope here so the change stays minimal and predictable.

Configuration

In <townRoot>/settings/config.json or <rigPath>/settings/config.json:

{ "effort_lock": false }

Testing

• go test ./internal/config/... — green, including the two new test cases.
• Manual: with effort_lock: false in town settings, started a Claude session and ran /effort high in-chat — applied successfully (no override message). With the setting removed, the override message returns.

Checklist

• Code follows project style.
• No breaking changes — default behavior preserved (EffortLock nil → locked, same as before).
• Tests cover both branches and the default.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 80.00000% with 2 lines in your changes missing coverage. Please review.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
internal/config/loader.go	75.00%	1 Missing and 1 partial ⚠️

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