feat(core): refactor project copies for v2

[jlongster]

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

Makes project-copy behavior location-aware so each core location owns its strategy registry. Strategy IDs are now open strings, while the built-in Git worktree implementation registers through the same internal registry.

Project directory persistence is centralized in ProjectDirectories. The database now stores a nullable strategy instead of main / root / git_worktree directory types. Existing classifications are intentionally cleared by the migration and repopulated by project refresh. Refresh discovers ordinary Git roots and strategy-managed copies, updates changed strategies, and removes missing paths.

Create, remove, and refresh are exposed through the V2 server with LocationMiddleware. Legacy OpenCode keeps only the LLM-backed name-generation endpoint so the TUI can generate a name first, then create the copy through the location-aware API.

The move-session dialog now uses the canonical project directory list, keeps the current checkout grouped separately, sorts other checkout roots before managed copies, and only enables deletion for non-current strategy-managed copies.

How did you verify your code works?

• bun typecheck in packages/core
• bun typecheck in packages/server
• bun typecheck in packages/opencode
• bun typecheck in packages/tui
• bun test test/project-directories.test.ts test/project-copy.test.ts in packages/core
• bun test test/server/project-copy.test.ts in packages/opencode
• bun run migration --check in packages/core
• Regenerated the JavaScript SDK with ./packages/sdk/js/script/build.ts

Screenshots / recordings

Not included.

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR