Speed up MIB compilation with IndexedFileReader

[FlorianVeaux]

Summary

• Replace pysmi's FileReader with a custom _IndexedFileReader that indexes the source directory once at construction, then does O(1) dict lookups instead of scanning the filesystem on every MIB lookup
• Profiling showed FileReader.get_subdirs() consumed 89% of compilation time — 1.7M stat() calls for just 20 MIBs, repeated for every single getData() call across 11,436 MIBs
• _IndexedFileReader delegates to pysmi's get_mib_variants() for fuzzy matching so behavior is identical to the stock reader

Result: compilation of 11,436 MIBs goes from ~60 min → ~8 min

Test plan

• Run invoke generate-traps-db on the full 11,436 MIB corpus
• Diff output dd_traps_db.json against committed version — zero missing MIBs, identical coverage
• Verified with cProfile that get_subdirs is no longer in the hot path

🤖 Generated with Claude Code

[github-actions]

⚠️ Recommendation: Add qa/skip-qa label

This PR does not modify any files shipped with the agent.

To help streamline the release process, please consider adding the qa/skip-qa label if these changes do not require QA testing.

[chatgpt-codex-connector]

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.05%. Comparing base (f410c11) to head (3ef21db).
⚠️ Report is 3 commits behind head on master.

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