new: Match package import paths in Go relationship inference

[jonpoole-fluidstack]

Moon's Go relationship inference resolves go list -deps output by module path only, so a repo where all projects share one go.mod (like systems) can never infer a project→project edge — every internal package collapses to the root module path (upstream context: moonrepo/moon#2360).

This adds a fallback: each project gets a package prefix — its own go.mod module path, or the nearest ancestor go.mod's module path joined with the project's relative directory — and go list entries that module matching can't resolve are matched by longest import-path prefix instead. go list now emits {{.Module.Path}}|{{.ImportPath}} pairs so both matching modes share one invocation.

	before	after
multi-module workspace (go.work)	edges via module …	unchanged (module match takes precedence)
single-module repo	no edges	edges via package …, e.g. a → b (production)

Non-obvious decisions:

• Based on the go_toolchain-v1.4.4 tag, not master — master needs proto ≥0.60 / moon 2.5 APIs; this branch builds and loads under moon 2.4.5 for local verification against a real workspace.
• Import-path edges use the moon project id directly (single-module projects have no alias to resolve through).
• Edges are deduped per target project, module match first — so existing multi-module behavior and via strings are byte-identical (all 29 pre-existing tests pass unchanged; +1 new single-module test).

Verified end-to-end on a demo single-module workspace: moon project a now reports Depends on: b (production), and touching libs/b marks a affected in moon query projects --affected.

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