perf: typed MapKey enum removes routing-tsp str(j) tax on numeric maps

[danieljohnmorris]

Summary

Adds a typed MapKey { Text(String), Int(i64) } to ilo's map representation. Before this change, Value::Map was keyed by String, so any program iterating a map by a numeric index had to call k=str j before every mget/mset. The routing-tsp benchmark (and any agent-written code that builds an index lookup table) paid that tax on every iteration.

With typed keys: mset m 7 v and mget m 7 work directly. Floats floor to i64 at the builtin boundary (matching at xs i); NaN/Infinity raise a runtime error. Text and Int are distinct keys: Int(1) and Text("1") no longer collide. Bool keys are stringified to Text (a bool map is always shorter as a two-arm ?, so the surface syntax isn't worth the lexer ambiguity).

JSON serialisation stringifies numeric keys (JS/Python convention). The round-trip remains lossy, since JSON object keys are always strings, deserialising back to a Record with text fields.

Repro before/after

Before (routing-tsp pattern):

loop>n;m=mmap;j=0;@<j 10{k=str j;m=mset m k j;j=+j 1};r=mget m (str 5);?r{n v:v;_:-1}

After: no stringification needed.

loop>n;m=mmap;j=0;@<j 10{m=mset m j j;j=+j 1};r=mget m 5;?r{n v:v;_:-1}

What's in the diff

• interpreter: introduce typed MapKey enum for Value::Map (280e389): Value::Map becomes Arc<HashMap<MapKey, Value>>. Adds MapKey::from_value for the builtin boundary, Ord for deterministic mkeys/mvals order, and stringifies numeric keys on to_json.
• vm: thread MapKey through bytecode and Cranelift JIT (1f4a547): HeapObj::Map switches to HashMap<MapKey, NanVal>. OP_MGET/MSET/MHAS/MDEL/MKEYS/MVALS build typed keys via new nanval_to_map_key helper. RC=1 in-place mset fast path is preserved. JIT helpers now report runtime errors on bad key types (matching tree/VM).
• verify: infer map key type from declarations and builtin args (192390e): drops the hard-coded "key must be t" constraint; mkeys returns L<declared-key-type>; frq xs:L a yields M a n.
• test + example: cross-engine coverage for typed map keys (63999b3): 15 new cross-engine tests; new examples/numeric-map-keys.ilo; updated regression_frq and examples/frq.ilo for the typed-key semantics.

Test plan

• cargo fmt --check clean
• cargo build --release --features cranelift clean
• cargo test --release --features cranelift passes (full suite green: ~2900 lib tests + every integration crate)
• cargo clippy --release --features cranelift --all-targets -- -D warnings clean
• examples/numeric-map-keys.ilo exercises all five entry points across tree, VM, and cranelift
• regression_numeric_map_keys covers mset, mget, mhas, mdel, mkeys, mvals, len, jdmp, float-floor, Int-vs-Text distinctness across all three engines

Follow-ups

• The from_json path still produces Record for generic objects rather than Value::Map. That's untouched here, but if/when the JSON shape grows a M n _ variant, we'd want to populate MapKey::Int from numeric-looking string keys.

[codecov]

Codecov Report

❌ Patch coverage is 72.14485% with 100 lines in your changes missing coverage. Please review.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
src/interpreter/mod.rs	72.13%	34 Missing ⚠️
src/verify.rs	65.65%	34 Missing ⚠️
src/vm/mod.rs	73.33%	32 Missing ⚠️

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