lexer: accept camelCase at post-dot field access

[danieljohnmorris]

Summary

Real-world JSON from NVD, AWS, Stripe, and GitHub is overwhelmingly camelCase. record.baseSeverity used to trip ILO-L003: unexpected character at the lexer because any uppercase mid-ident was a hard error. The workaround (jpth! record "baseSeverity") is verbose and burns tokens on every field read, which fights the manifesto: agents reading JSON shouldn't pay a token tax for the fact that the source happens to capitalise.

This mirrors the snake_case post-pass that landed earlier: at post-dot field-access position (and only there), the lexer absorbs the camelCase tail into a single Ident token. Bindings still emit ILO-L003 unchanged.

Repro

Before:

$ ilo 'f j:t>R n t;r=jpar! j;r.baseSeverity' f '{"baseSeverity":"HIGH"}'
ILO-L003: unexpected token 'baseSeverity'

After:

$ ilo 'f j:t>R n t;r=jpar! j;r.baseSeverity' f '{"baseSeverity":"HIGH"}'
HIGH

Bindings still reject (unchanged):

$ ilo 'fooBar=5;fooBar'
ILO-L003: unexpected token 'fooBar'

What's in the diff

• lexer: accept camelCase at post-dot field access - the fix itself. Two lex paths needed updating: the type-sigil branch (L/R/F/O/M/S tokens, e.g. the S in baseSeverity) and the single-uppercase-error branch (non-sigil capitals, e.g. the U in gitURL). New prev_ident_is_post_dot helper detects the position; new absorb_camel_tail does the merge and advances the logos cursor.
• test: cross-engine regression coverage for camelCase dot-access - 20 tests across tree, VM, and Cranelift covering sigil capitals, non-sigil capitals, chained access, trailing digits, safe access, mixed camel + snake (gitURL_count), and negative regressions on bindings.
• example: camelCase dot-access on real-world JSON shapes - picked up by tests/examples_engines.rs so every engine exercises the path through the example harness too.

Test plan

• cargo build --release --features cranelift
• cargo test --release --features cranelift (4101 passed, 0 failed, up from 4081 with 20 new)
• cargo fmt
• cargo clippy --release --features cranelift -- -D warnings (clean)
• Manual repro of baseSeverity, gitURL, chained, safe, mixed, and binding-still-errors cases

Follow-ups

• Leading-uppercase keys like record.URL and record.ID still fail at the lexer (no preceding Ident to merge into). Worth a separate fix that treats Dot+uppercase-run as a field-name Ident directly. Out of scope here to keep the change tight.

[codecov]

Codecov Report

❌ Patch coverage is 92.39130% with 7 lines in your changes missing coverage. Please review.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
src/lexer/mod.rs	92.39%	7 Missing ⚠️

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