perf(forge): avoid compiling for doc generation

[figtracer]

Summary

• Configure the bundled, in-process Solar parser directly for forge doc, avoiding the ABI-only compiler process when every Solidity source is Solar-compatible.
• Preserve existing behavior for pre-0.8, mixed-version, and Solidity-free projects through the compiler-backed fallback, and honor configured skip filters on the fast path.
• Add regression coverage proving the fast path neither invokes solc nor documents skipped sources, while empty and mixed-version projects retain their fallback behavior.

Benchmarks

Benchmarked release builds on Solady with 277 Solidity files. Each sample removed out, cache, and both generated doc directories:

hyperfine --warmup 1 --runs 10 \
  --prepare 'rm -rf out cache /tmp/solady-doc-before /tmp/solady-doc-after' \
  'forge-before doc --out /tmp/solady-doc-before --quiet' \
  'forge-after doc --out /tmp/solady-doc-after --quiet'

Before: 1.412 s ± 0.032 s
After:  135.8 ms ± 8.9 ms
Speedup: 10.40x

The generated documentation is identical according to diff -qr.

[mattsse]

lgtm

[mablr]

Cool, big gain on big projects like aave-v4.