refactor: Route residual task behavior by capability (#13595)
## Intent
Remove residual task and execution behavior selected by contributor
provenance.
## Changes
- Route generic argv overrides through one core path, including
pure-native roots.
- Add explicit `Unknown`/`Include`/`Exclude` dependency source
participation to task contracts.
- Mark Cargo automatic inputs untracked when dependency participation is
unknown, preventing fail-open caching.
- Make normal and pre-parsed JavaScript discovery attach explicit
JavaScript contracts.
- Default omitted contracts to empty behavior without consulting
`ToolchainId`.
- Keep pre-parsed package-json input on the typed JavaScript contributor
while additional contributors discover normally.
- Update architecture and API documentation.
## Testing
- `cargo test -p turborepo-repository` (384 passed before rebase;
focused task/builder tests passed after rebase)
- `USER=opencode cargo test -p turborepo-task-executor` (21 passed)
- `cargo test -p turborepo-engine` (126 passed)
- `cargo test -p turbo --test cargo_workspace_test` (57 passed)
- `cargo clippy -p turborepo-repository -p turborepo-task-executor -p
turborepo-engine --all-targets -- -D warnings`
- Pre-push `format` and `check:toml` hooks
Advances TURBO-5798.
