Add auto-import operation completion

[itsfuad]

Goal

Add auto-import support for operation completion after . and |>.

Required design

• Extend operation discovery beyond current module and direct imports without rescanning dependency graph per request.
• Preserve defining module, canonical module identity, import path, export visibility, and symbol identity in semantic operation catalog.
• Generate import edits together with syntax-correct dot and pipe call edits.
• Handle aliases, existing imports, name collisions, duplicate candidates, unavailable symbols, and private symbols deterministically.
• Keep current-module methods separate from importable free functions.
• Reuse cursor-local semantic context and indexed prefix lookup.

Constraints

• Do not re-resolve symbols in LSP.
• Do not mutate shared generic symbols with call-site types.
• Do not replace non-empty argument lists.
• Keep UTF-16 edit ranges and isolated completion compilation correct.
• Reuse package resolver identity; do not create LSP-specific version resolution. Future MVS work is tracked by Adopt Go-style module version selection #58.

Relationships

• Add free builtins and pipe call support #76 and PR Add free builtins and pipe call support #77 delivered free operations, pipe calls, and indexed semantic operation discovery.
• Adopt Go-style module version selection #58 owns future canonical module version selection consumed by import resolution.

Validation

• Completion tests for unimported workspace and dependency functions.
• Existing import, alias, collision, private symbol, and duplicate-path cases.
• Applied-edit tests for dot and pipe syntax with empty and non-empty calls.
• Large-catalog regression proving completion does not walk every module symbol.
• LSP race test and bundled source fixture.