feat: Add Go external resolution fingerprints (#13957)
<!-- CURSOR_AGENT_PR_BODY_BEGIN -->
### Description
Add a Go external-resolution domain backed by readonly Go module graph
and checksum data. Build per-module transitive external closures and a
workspace aggregate while retaining workspace modules as internal
relationships.
Include applicable Go definition and checksum sources, deterministic
replacement identities, and explicit errors for unresolved graph
entries.
Closes TURBO-5960
### Testing Instructions
```bash
cargo test -p turborepo-repository --lib go::tests::external_resolution
cargo test -p turborepo-repository --lib go::tests
cargo test -p turborepo-repository --lib
cargo fmt --all --check
cargo lint
```
<!-- CURSOR_AGENT_PR_BODY_END -->
<div><a
href="https://cursor.com/agents/bc-93321fc5-6d9e-4a4a-b939-cfd623df17d1?cursor_ref=pr_footer&cursor_cta=open_in_web"><picture><source
media="(prefers-color-scheme: dark)"
srcset="https://cursor.com/assets/images/open-in-web-dark.png"><source
media="(prefers-color-scheme: light)"
srcset="https://cursor.com/assets/images/open-in-web-light.png"><img
alt="Open in Web" width="114" height="28"
src="https://cursor.com/assets/images/open-in-web-dark.png"></picture></a> <a
href="https://cursor.com/background-agent?bcId=bc-93321fc5-6d9e-4a4a-b939-cfd623df17d1&cursor_ref=pr_footer&cursor_cta=open_in_cursor"><picture><source
media="(prefers-color-scheme: dark)"
srcset="https://cursor.com/assets/images/open-in-cursor-dark.png"><source
media="(prefers-color-scheme: light)"
srcset="https://cursor.com/assets/images/open-in-cursor-light.png"><img
alt="Open in Cursor" width="131" height="28"
src="https://cursor.com/assets/images/open-in-cursor-dark.png"></picture></a> </div>
---------
Co-authored-by: Cursor Agent <cursoragent@cursor.com>
