bundler: handle keep-names edge cases

[in0vik]

What does this PR do?

Small follow-up to #40503 for three keepNames edge cases:

• Count the synthetic __name() read so minification cannot inline away a block-scoped function binding.
• Preserve inferred names through ??=, ||=, and &&= assignments.
• Leave user-defined static name methods, accessors, and fields intact.

The patch adds focused runtime tests and keeps the existing tree-shaking test unchanged.

How did you verify your code works?

• BUN_EXE="$PWD/build/debug/bun-debug" ./build/debug/bun-debug test test/bundler/bundler_minify.test.ts — 51 pass, 0 fail.
• git diff --check b406b4bd..HEAD — clean.

Merge Danger

Door: Two-way. Blast radius: keepNames output and the __name runtime helper. This targets the feature branch, so #40503 can absorb or adjust it before landing on main.

[claude]

Claude Code Review

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