Fix hardcoded source ID in bugc debug info

[gnidan]

Summary

The compiler was hardcoding source ID as "0" in three places when generating ethdebug/format debug info:

• irgen/generate/module.ts — variable declaration source ranges
• irgen/generate/process.ts — code context source ranges (was using module name instead of source ID)
• evmgen/program-builder.ts — contract definition source range

This PR threads sourcePath from the compilation input through the IR generation state (State.Module.sourceId) and into Ir.Module.sourceId, which is then used consistently across all debug info output. When no sourcePath is provided (e.g. in tests), it falls back to "0".

Changes:

• Add sourceId field to Ir.Module and State.Module
• IR gen pass accepts sourcePath from sequence state, defaults to "0"
• process.ts code contexts use sourceId instead of module name
• program-builder.ts reads sourceId from IR module
• Update all test module constructions with sourceId field
• Add 2 new tests verifying default and explicit sourceId behavior

[github-actions]

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2026-03-09 20:12 UTC

[gnidan]

Review (debugger agent): Approve.

The fix correctly threads sourcePath through the compiler pipeline:

1. CLI passes filePath as sourcePath through the pass system
2. generateModule() accepts optional sourcePath, defaults to "0" for backward compatibility
3. Ir.Module.sourceId stores the actual source identifier
4. buildProgram() uses ir.sourceId instead of hardcoded "0" for the debug info source.id
5. Process.buildContextForNode uses sourceId from current module instead of module.name

The sourceId is also correctly propagated through optimizer cloning (BaseOptimizationStep) and all test fixtures updated with the new required field.

This matters for pointer dereferencing — when programs-react resolves variables, the source.id in Materials.SourceRange needs to match actual source identifiers for correct source mapping. LGTM.