#14810: fix:sandbox file path Inconsistency

<!-- greptile_comment --> <h2>Greptile Overview</h2> <h3>Greptile Summary</h3> This PR adds a sandbox path resolver to translate container paths (e.g. `/workspace/...`) into host workspace paths, and wires it into `runMessageAction` so outbound actions can accept sandbox-style file parameters (`filePath`, `path`, `media`). It also exports the new resolver utilities via the plugin SDK and adds unit tests for the resolver behavior. <h3>Confidence Score: 3/5</h3> - This PR is close, but has at least one definite TypeScript test failure and a concrete path-resolution logic bug that can mis-rewrite certain absolute paths. - Core change is small and localized, but the new test file uses an invalid `SandboxWorkspaceInfo` shape (will not typecheck) and the resolver’s `startsWith` check will incorrectly rewrite paths that share a prefix with the container workdir (e.g. `/workspace2/...`). - src/infra/outbound/sandbox-path-resolver.ts, src/infra/outbound/sandbox-path-resolver.test.ts <!-- greptile_other_comments_section --> _{(2/5) Greptile learns from your feedback when you react with thumbs up/down!} <!-- /greptile_comment -->