Index workspace references beyond the open-root import closure

Summary

Make references and rename aware of source-root modules outside the current open-root import closure.

Today the LSP matches canonical SemanticOccurrence identities across the accepted ProjectAnalysis, which contains open roots and their outgoing imports. A closed module that imports the selected declaration is invisible unless some open root reaches it.

Scope

• Add immutable per-module resolved-use summaries keyed by canonical semantic identity.
• Maintain a workspace reference layer separately from the lightweight export inventory and current semantic project snapshot.
• Use the import inventory introduced by #178 to derive reverse dependents and narrow semantic work.
• Refresh reference summaries lazily or through bounded background work.
• Retain use context, not just location:
  • declaration
  • import
  • direct call
  • first-class value
  • run subject
  • type use
  • read/write/move/drop
• Preserve open-buffer precedence and accepted-revision coherence.
• Define explicit freshness/completeness states so read-only references do not silently imply a complete rename.
• Require complete, current, editable coverage before producing workspace rename edits.

Acceptance criteria

• References to a top-level declaration include uses from closed reverse-dependent source-root modules.
• Locals, parameters, and pattern bindings remain module/function-local.
• Results are keyed by semantic identity rather than spelling.
• File create/change/delete/rename and import-edge changes invalidate only affected summaries.
• The reference query reports or withholds incomplete results according to a documented freshness policy.
• Rename cannot return a partial workspace edit when a relevant module is stale or uneditable.
• Unsaved open buffers override on-disk summaries.
• Generated-workspace tests cover reverse-dependency narrowing and per-module reuse.

Architecture constraints

• Do not fold semantic occurrences into the header-only WorkspaceInventory.
• Do not make every file a permanent ProjectAnalysis root.
• Treat persistence as a later profiling-driven startup optimization.

Start by reading the current ProjectAnalysis, lightweight WorkspaceInventory, and the import inventory introduced by #178 to understand existing scope and reverse-dependent discovery. Define the freshness policy and per-module reference summaries, then use the generated-workspace tests to verify narrowing, invalidation, open-buffer precedence, complete rename coverage, and reuse.