fix(gateway): clear claude-cli session on sessions.reset RPC

[zezaeoh]

What

sessions.reset (JSON-RPC) only reset the native session store. For claude-cli-backed agents the actual conversation lives in the Claude CLI session files (.jsonl + CLAUDE.md), which were left in place — so the next turn resumed stale history despite a "reset".

The /reset chat command already clears these via providers.ResetCLISession (handleResetCommand in cmd/gateway_consumer_handlers.go). This brings the RPC path to parity with the chat command.

Change

• handleReset now also calls ResetCLISession("", key), mirroring the chat path. It is a no-op when the CLI provider is not in use (the helper guards on missing files).
• The call is wired through an overridable package var (cliSessionReset) so the behavior can be regression-tested without filesystem side effects.

Test

• New TestSessionsReset_ClearsCLISession asserts the RPC reset invokes the CLI clear with the correct session key and still resets the native store.
• go test ./internal/gateway/methods/ ✓, go vet ./internal/gateway/methods/ ✓, gofmt clean.

Notes

• No overlap with the currently open reset-related PRs (fix(cron): always reset session before cron runs — stateless flag inverted #1032 / fix(cron): invert stateless gate to match UI label #1139 cron stateless gate, feat(ui): add Compact button to session detail page #1117 UI compact button) — none touch the RPC CLI-clear path.
• Follow-up to fix(gateway): inject agent key in MCP bridge so session tools resolve identity #1197 (same sessions/bridge area, separately scoped).

[mrgoonie]

Summary: This brings the JSON-RPC sessions.reset path into parity with the chat /reset command by clearing the Claude CLI session files as well as the native session store.

Risk level: Low

Mandatory gates:

• Duplicate/prior implementation: clear — search found no existing PR/issue implementing this RPC-specific reset path; the only prior implementation is the chat-command path this mirrors.
• Project standards: passed — small gateway-method change, provider helper reuse, and regression test fit the surrounding session-method patterns.
• Strategic necessity: clear value — without this, web/RPC reset can leave claude-cli-backed agents resuming stale .jsonl/CLAUDE.md history despite reporting reset success.
• CI/checks: green — release-versioning, go, and web checks succeeded.

Findings:

• Critical: none
• Important: none
• Suggestion: none

Verdict: APPROVE

Evidence checked: internal/gateway/methods/sessions.go, internal/gateway/methods/sessions_reset_cli_test.go, existing /reset implementation in cmd/gateway_consumer_handlers.go, providers.ResetCLISession behavior in internal/providers/claude_cli_session.go, duplicate search, and local go test ./internal/gateway/methods/.