fix(p2-json-errors): remove safe-but-flagged unwrap in is_type_id_value

[brettdavies]

Summary

Addresses the json_errors.rs:192 finding from PR #80's dogfood run: the .unwrap() on trimmed.chars().next() inside is_type_id_value was provably safe (an is_empty() guard ten lines earlier guarantees at least one char), but the code-unwrap source audit pattern-matches on .unwrap() call expressions and surfaced it during self-dogfood.

Replaces the .unwrap() with a let-else that returns false, consistent with the function's "return false on any invalid input" pattern. Adds a comprehensive unit test (is_type_id_value_validates_json_shapes) covering all five non-string JSON value kinds (Number, Bool, Null, Array, Object), three valid identifier shapes (kebab-case, SCREAMING_SNAKE, snake_case), and three invalid string shapes (whitespace, period-separated, leading digit).

Changelog

Fixed

• Fix code-unwrap self-dogfood finding at json_errors.rs:192: replace .unwrap() with a let-else returning false in is_type_id_value.

Type of Change

• fix: Bug fix (non-breaking change which fixes an issue)

Related Issues/Stories

• PR fix(code-unwrap): cfg(not(test)) polarity; add missing negative-case tests #80 (dogfood surfaced json_errors.rs:192 as the one remaining code-unwrap finding)
• PR fix(audits): exempt #[cfg(test)]-gated items from code-unwrap #77 (introduced the code-unwrap audit)
• PR feat(audits): role-based JSON error envelope validation #79 (introduced the .unwrap() that this PR removes)

Testing

• Unit tests added/updated
• All tests passing

Test Summary:

• cargo test: 848 passed, 2 ignored (8 suites). +1 new test is_type_id_value_validates_json_shapes in src/audits/behavioral/json_errors.rs.
• cargo clippy --all-targets -- -Dwarnings: clean.
• cargo fmt --check: clean.

Files Modified

Modified:

• src/audits/behavioral/json_errors.rs: replace .unwrap() with let-else at line 192; add is_type_id_value_validates_json_shapes unit test.

Created:

• None.

Renamed:

• None.

Deleted:

• None.

Breaking Changes

• No breaking changes

Deployment Notes

• No special deployment steps required

Checklist

• Code follows project conventions and style guidelines
• Commit messages follow Conventional Commits
• Self-review of code completed
• Tests added/updated and passing
• No new warnings or errors introduced
• Changes are backward compatible