Extend inline meta continuations

[adamcavendish]

Summary

• allow inline $for and $if to continue after safe newline punctuation: = and |
• keep plain newline $for/$if statement-level after Python colons, nullable ?, and comma-separated declarations
• improve $for option diagnostics and document inline separator examples

Verification

• cargo test
• just lint
• cargo fmt --check
• git diff --check
• cargo run --example inline_control_flow
• cargo run --example macro_features
• mdbook build docs
• isolated mdbook test docs -L <isolated>/debug/deps
• Codex review gate: PASS, no [P1] findings

[codecov-commenter]

⚠️ Please install the to ensure uploads and comments are reliably processed by Codecov.

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ All tests successful. No failed tests found.
❗ Your organization needs to install the Codecov GitHub app to enable full functionality.

🚀 New features to boost your workflow:

• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.