`@wraith-protocol/codemod` package for v0.x -> v1.0 migrations

[truthixify]

Tier: M (2-4 days) | Type: dx

Context. MIGRATING.md documents the v0.x -> v1.0 surface changes prose-first, but partners upgrading real apps still need to grep-and-sed by hand. A jscodeshift-based codemod package would automate the mechanical renames (import paths, deprecated names, Announcement shape drift) and let us keep future majors cheap.

Scope.

• New workspace package packages/codemod/ with a CLI (npx @wraith-protocol/codemod v1).
• One transform per breaking change in MIGRATING.md: import moves, renames, type widenings.
• Snapshot tests over a fixture directory of pre / post files.
• Doc'd in MIGRATING.md above the manual instructions.

Acceptance.

• CLI runs against a fixture app and produces the expected diff
• Every transform has a fixture with pre / post snapshot
• Idempotent: running twice leaves the second pass a no-op
• Published under the workspace but not required by consumers

Files. packages/codemod/ (new), packages/codemod/transforms/v1/ (new), packages/codemod/fixtures/ (new), MIGRATING.md.