[Elizabeth Craig (ecraig12345)]

Follow-up from #1233: Probably due to various feature additions over time, the lage CLI was doing a lot of redundant git operations on startup, which could be a major startup performance hit in huge repos where git is very slow or if there are a lot of changes.

User-facing impact

• Only do the process of getting branch and local changes from git once (shared between --since filtering and target graph creation) for run, info, and affected.
• Combine getting staged, unstaged, and untracked changes into a single git operation.
• Make affected use the same initial package-selection policy as run and info, including configured ignore patterns and --to handling (skips change detection).
• Changes matching repoWideChanges now include staged, unstaged, and untracked files in addition to committed branch changes (so uncommitted repo-wide changes can expand a --since run to all packages, matching the target hashing/caching behavior).
• Match repoWideChanges against paths returned by git, not against files on disk. This is more efficient and ensures deleted files match.
• Avoid unnecessary git change scans for run/info with --scope/--to: only scan if --since is set and one or more staged targets is configured.

Internal changes

• Replace getRepoChanges with getChangedFiles, collecting each branch changes and all other changes once and deduplicating paths into one snapshot.
• Add getWorkingTreeChanges helper (used above) to get staged/unstaged/untracked files in a single git operation.
• Use a discriminated ChangedFiles union with skipped, failed, and success statuses (success also includes file paths).
• Update getFilteredPackages and createTargetGraph to accept a changes?: ChangedFiles option and skip git detection internally.
• getFilteredPackages internally handles combining CLI/config ignores and normalizing --to as scope without dependents.
• Add createFilteredTargetGraph for run and info. It checks both root pipeline and package-level lage definitions for staged configuration (to determine if git changes are needed), shares a git snapshot between filtering and graph construction when needed, and returns { packages, targetGraph }.
• affected continues to only get the filtered packages (not a full target graph). The lage service continues building a reusable graph without staged-target optimization.
• Consolidate run's watch and regular mode into run/action.ts to dedupe code and prevent accidental behavior differences.
• Allow getPackagesByFiles to reuse preloaded PackageInfos. Clarify that its all-package fallback applies when any non-ignored file belongs to no package.

[Elizabeth Craig (ecraig12345)]

This is the same content as the previous runAction and watchAction, with deduped setup and using new helpers.