REST + CLI mirror for loopover_propose_action

[JSONbored]

Context

The MCP tool loopover_propose_action (src/mcp/server.ts:2502, via proposeAction at src/mcp/server.ts:4109-4137) stages a new pending agent action for later maintainer approval (never auto-executes) via createPendingAgentActionIfAbsent. REST already has the accept/reject side (POST /v1/repos/:owner/:repo/agent/pending-actions/:id/:decision) and the list side (GET .../agent/pending-actions), both CLI-mirrored, but no REST route exists to CREATE a new staged action, and no maintain propose CLI subcommand exists.

Requirements

• Add POST /v1/repos/:owner/:repo/agent/pending-actions in src/api/routes.ts, requireRepoManageAccess/requireRepoWriteAccess-gated, calling createPendingAgentActionIfAbsent with the head-SHA pinning proposeAction already does (src/mcp/server.ts:4118-4127).
• Add maintain propose <action-class> <pull-number> [--reason ...] CLI subcommand.

Deliverables

• POST /v1/repos/:owner/:repo/agent/pending-actions route
• maintain propose CLI subcommand
• Unit test

Test Coverage Requirements

99%+ Codecov patch coverage on every changed line and branch in the new route/tool/CLI code, plus a test asserting output parity between the mirrored surfaces for identical input.

Expected Outcome

A new pending agent action can be staged over REST/CLI, completing the create/list/decide trio that only had list/decide before.

Links & Resources

Precedent: the sibling decision route/CLI pair (src/api/routes.ts:2593, loopover-mcp.js:2753-2760).

[linear-code]

JSO-4558