#13215: fix: pass agentId to loadCostUsageSummary in /usage cost command

## Problem When using named agents (not `main`), the `/usage cost` command shows **$0 for all time ranges** because `loadCostUsageSummary()` defaults to `agentId="main"` and scans `~/.openclaw/agents/main/sessions/` instead of the correct agent folder. ## Root Cause In `src/auto-reply/reply/commands-session.ts`, the `/usage cost` handler calls: ```typescript const summary = await loadCostUsageSummary({ days: 30, config: params.cfg }); ``` Without passing `agentId`, `loadCostUsageSummary` defaults to `main` (line 399 in `src/infra/session-cost-usage.ts`): ```typescript const sessionsDir = resolveSessionTranscriptsDirForAgent(params?.agentId); ``` ## Solution Resolve `agentId` from `params.sessionKey` before calling `loadCostUsageSummary`: ```typescript const agentId = params.sessionKey ? resolveAgentIdFromSessionKey(params.sessionKey) : undefined; const summary = await loadCostUsageSummary({ days: 30, config: params.cfg, agentId }); ``` ## Impact ✅ **Fixes**: - `/usage cost` now shows correct totals for non-main agents - 1-day, 7-day, 30-day ranges all work correctly - Dashboard cost panel displays accurate usage ✅ **Unchanged**: - Per-session cost already worked (uses direct file path) - Global `usage.cost` gateway handler intentionally unchanged (may aggregate across all agents) ## Testing - [x] Code follows project style - [ ] Tested with custom agent name (requires non-main agent setup) - [ ] Verified cost totals match transcript JSONL files ## References Fixes #13173 <!-- greptile_comment --> <h2>Greptile Overview</h2> <h3>Greptile Summary</h3> This PR fixes `/usage cost` for non-`main` agents by resolving the agent id from `params.sessionKey` and passing it into `loadCostUsageSummary()`, so the cost scan reads from the correct agent’s sessions directory. The change is localized to the command handler and aligns with the existing default behavior in `loadCostUsageSummary` (still defaults to `main` when `agentId` is omitted/undefined), keeping the gateway/global usage handler behavior unchanged. <h3>Confidence Score: 5/5</h3> - This PR is safe to merge with minimal risk. - The change is small, localized, and uses existing sessionKey parsing/normalization utilities; it preserves default behavior when sessionKey is absent and does not affect other `loadCostUsageSummary` call sites. - No files require special attention <!-- greptile_other_comments_section --> _{(5/5) You can turn off certain types of comments like style [here](https://app.greptile.com/review/github)!} <!-- /greptile_comment -->