refactor: Use package knowledge for task hashing paths (#13461)
### Description
Part 6 of the package/scope knowledge completion stack.
Introduce graph-created task contexts that bind package identity,
repository root, authoritative directory, scope kind, and optional
compatibility payload. Task file hashing and dependency-output hashing
use these contexts while preserving exact hash bytes, including pure
Cargo root tasks.
### Testing Instructions
- `cargo test -p turborepo-task-hash`
- `cargo test -p turbo --test final_hash_contract`
- `cargo lint`
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Co-authored-by: Cursor Agent <cursoragent@cursor.com>
