implement exception __context__

[davidhewitt]

This PR implements exception __context__ attribute plus fixes various cases with bare raise that I (with Claude's help) found while doing so (see new test cases).

[codspeed-hq]

Merging this PR will not alter performance

✅ 17 untouched benchmarks
⏩ 15 skipped benchmarks¹

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_{Comparing dh/return-finally (bb2f70c) with main (1346bad)²}

Footnotes

1. 15 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

2. No successful run was found on main (788cffe) during the generation of this report, so 1346bad was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

[github-actions]

Codecov Results 📊

❌ Patch coverage is 67.82%. Project has 23474 uncovered lines.
✅ Project coverage is 65.05%. Comparing base (base) to head (head).

Files with missing lines (9)

File	Patch %	Lines
crates/monty/src/exception_private.rs	73.08%	⚠️ 14 Missing and 5 partials
crates/monty/src/bytecode/vm/exceptions.rs	58.06%	⚠️ 13 Missing and 4 partials
crates/monty/src/bytecode/compiler.rs	62.50%	⚠️ 12 Missing and 3 partials
crates/monty/src/heap.rs	37.50%	⚠️ 5 Missing and 2 partials
crates/monty/src/heap_traits.rs	42.86%	⚠️ 4 Missing and 1 partials
crates/monty/src/prepare.rs	73.33%	⚠️ 4 Missing and 1 partials
crates/monty/src/value.rs	0.00%	⚠️ 3 Missing
crates/monty/src/parse.rs	66.67%	⚠️ 1 Missing and 1 partials
crates/monty/src/bytecode/vm/mod.rs	100.00%	⚠️ 1 partials

Coverage diff

@@            Coverage Diff             @@
##          main       #PR       +/-##
==========================================
+ Coverage    64.95%    65.05%     +0.1%
==========================================
  Files          263       263         —
  Lines        66949     67171      +222
  Branches    143813    144258      +445
==========================================
+ Hits         43483     43697      +214
- Misses       23466     23474        +8
- Partials      3234      3248       +14

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Generated by Codecov Action

[codecov]

Codecov Report

❌ Patch coverage is 93.10345% with 12 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
crates/monty/src/heap.rs	62.50%	1 Missing and 2 partials ⚠️
crates/monty/src/value.rs	0.00%	3 Missing ⚠️
crates/monty/src/exception_private.rs	96.15%	0 Missing and 2 partials ⚠️
crates/monty/src/bytecode/vm/exceptions.rs	96.77%	1 Missing ⚠️
crates/monty/src/bytecode/vm/mod.rs	87.50%	0 Missing and 1 partial ⚠️
crates/monty/src/parse.rs	66.66%	0 Missing and 1 partial ⚠️
crates/monty/src/prepare.rs	93.33%	0 Missing and 1 partial ⚠️

📢 Thoughts on this report? Let us know!

[davidhewitt]

This is problematic because __context__ introduces heap references into RunError. Need a strategy to get that right before we proceed here.

[cubic-dev-ai]

No issues found across 16 files