Add inline snapshots (insta-style)

[MatthewMckee4]

Summary

• Add inline snapshot support via karva.assert_snapshot(value, inline="") where expected values live directly in test source files
• Source files are rewritten in-place with --snapshot-update, or .snap.new files with inline metadata are created for karva snapshot accept
• New karva_snapshot::inline module handles dedenting, string literal generation, source scanning, and file rewriting

Test plan

• Unit tests for dedent, generate_inline_literal, find_inline_argument, apply_edit
• Integration tests for inline snapshot creation, matching, mismatch, update, multiline, multiple per test, accept, reject, and pending flows
• just test passes (521 tests)
• prek run -a passes

🤖 Generated with Claude Code

[codspeed-hq]

CodSpeed Performance Report

Merging this PR will not alter performance

_{Comparing add-inline-snapshots (1d3fabc) with main (fc76cea)}

⚠️ Unknown Walltime execution environment detected

Using the Walltime instrument on standard Hosted Runners will lead to inconsistent data.

For the most accurate results, we recommend using CodSpeed Macro Runners: bare-metal machines fine-tuned for performance measurement consistency.

Summary

✅ 1 untouched benchmark