Add full workspace reference index

[sidux]

Summary

Adds a full workspace indexing mode that builds complete symbol maps and a cross-file reference candidate index in the background. Full indexing is now the default strategy, so new/missing config uses strategy = "full" automatically. Users can still opt into lighter modes with strategy = "composer", "self", or "none".

Key changes:

• Make indexing.strategy = "full" the default in config/schema/docs.
• Start a background full workspace index after normal initialization.
• Add a reference index keyed by classes, functions, constants, members, and Laravel string keys.
• Use full-index data broadly where it is available:
  • class, function, constant, member, constructor, Laravel-string references now snapshot only reference-index candidate files instead of snapshotting all user files and filtering afterward.
  • rename benefits through the same reference engine.
  • go-to-implementation and type-hierarchy subtype lookups use the reverse inheritance index (gti_index) once workspace indexing is ready.
• Batch workspace parsing and index publication to avoid thousands of per-file lock/update cycles.
• Use weighted, largest-first progress reporting so large files do not create a misleading late tail.
• Bulk-evict reference-index batches in one pass

[codecov-commenter]

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Codecov Report

❌ Patch coverage is 96.92005% with 47 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/references/mod.rs	93.90%	43 Missing ⚠️
src/parser/ast_update.rs	98.49%	4 Missing ⚠️

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