[cc] string interning

[jgarzik]

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[Copilot]

Pull request overview

This PR introduces a centralized string interning system to replace lexer-local identifier interning, improving memory efficiency and enabling O(1) string equality comparisons throughout the compiler.

Key Changes:

• New strings.rs module with StringId and StringTable for global string interning
• Replaced String with StringId in AST, types, and symbols for all identifier names
• Eliminated identifier ID remapping between tokenizer and preprocessor by sharing the StringTable

Reviewed changes

Copilot reviewed 8 out of 9 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
cc/strings.rs	New module providing StringId/StringTable interning infrastructure with pre-interned empty string
cc/token/lexer.rs	Replaced local IdentTable with StringTable reference, updated API to get/get_opt
cc/token/preprocess.rs	Removed ID remapping logic, pass shared StringTable to nested tokenizers
cc/types.rs	Changed member/tag names from String to StringId, updated find_member signature
cc/symbol.rs	Changed symbol names to StringId, made SymbolError Copy, updated lookup methods
cc/parse/ast.rs	Changed all name fields (Ident, Goto, Label, etc.) from String to StringId
cc/parse/parser.rs	Updated to work with StringIds, added get_ident_id helper, updated all tests
cc/linearize.rs	Added StringTable reference, converts StringIds to Strings at IR boundary
cc/main.rs	Creates shared StringTable and threads it through compilation pipeline

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