fix: multi-line bodies inside brackets, parens, and >> pipe chains

[danieljohnmorris]

Summary

Three persona-flagged shapes (Multi-line function bodies still fatal, L1310 quant-trader, L1325 re-flag, L938 db-analyst, plus the cross-persona summary at L1023) all came from one root cause: normalize_newlines injected a ; between tokens that weren't statement boundaries. Post-#168 the header→body case was fixed; this PR finishes the job for the remaining three shapes.

The token-cost framing: every persona who reached for natural indented body shapes paid a 5-minute debug-and-collapse tax, plus the ILO-P009 expected expression, got Semi at a column deep inside a continuation line obscured the real cause. Manifesto cost was real and repeated.

Repro before/after

Pre-fix, all three failed with ILO-P009:

g>L n
  xs=[
    1,
    2,
    3
  ]
  xs

gp x:n>n
  y=(+x
    1)
  y

pipe x:n>n
  x
    >>str
    >>len

Post-fix, all three run on tree, vm, and cranelift.

What's in the diff

• c2c28d4 lexer: suppress newline-to-semi inside ( ) and [ ] and after >>. normalize_newlines tracks (/[ depth and treats newlines inside as a single space (so (+x\n 1) doesn't normalise to (+x1)). Continuation lines that start with >> (the only operator that's never a valid statement start) suppress the ; too; +/-/* etc. are valid prefix-call heads and stay untouched. String walking is pre-existing from fix: comments above bound-call lines no longer corrupt parsing #236; this PR just relies on it so brackets inside text don't bump depth.
• 103d877 test: cross-engine coverage. Six new shapes in regression_multiline_fn_body.rs (multi-line list, leading-comma list, multi-line paren, multi-line pipe, nested ( inside [, pipe chain inside a {...} loop body) across tree/vm/cranelift. New examples/multiline-bodies.ilo so the example_engines harness exercises the same shapes and an agent reading examples sees indented bodies as canonical.

Test plan

• cargo test --release --features cranelift --test regression_multiline_fn_body — 3 tests across tree/vm/cranelift, all green
• cargo test --release --features cranelift --test examples_engines — examples harness green including new file
• cargo test --release --features cranelift full suite — 2871 lib passed, 0 failed; all integration tests green
• cargo fmt --check
• cargo clippy --release --features cranelift --all-targets

Out of scope

Pattern 4 from the investigation (indented -- comments above paren-bound calls) was already in flight on fix/comment-parse-corrupt and shipped in #236 before this PR landed. The two changes coexist; this PR rebased onto the merged #236.

Follow-ups

• Single-pass indent skip would shave one cheap iterator-clone per indented newline. Deferred as nice-to-have.
• The misleading caret-column complaint is partially fixed (because the spurious ; no longer lands inside a continuation) but a full span-rewrite is a separate piece of work.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ All tests successful. No failed tests found.

📢 Thoughts on this report? Let us know!