Feat/serde bridge (7/8)

[bnomei]

Linked Issue

Closes #

Description

Add a serde_json-style API bridge on top of the existing encode/decode pipeline. This introduces to_string/from_str/to_vec/to_writer/from_reader APIs plus option-aware variants, re-exports them at the crate root, and documents the usage. Tests cover round-trips, IO helpers, and option wiring. This is PR 7 of 8 in the intended sequence (1-8).

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Refactoring (no functional changes)
• Performance improvement
• Test coverage improvement

Changes Made

• Add serde-style to/from string/slice/reader/writer APIs plus option-aware variants.
• Re-export the new API at the crate root and add docs/examples.
• Add serde API tests for round-trips, IO, and option wiring.

SPEC Compliance

• This PR implements/fixes spec compliance
• Spec section(s) affected:
• Spec version:

Testing

• All existing tests pass
• Added new tests for changes
• Tests cover edge cases and spec compliance

Tests run: cargo test

Pre-submission Checklist

• My code follows the project's coding standards
• I have run code formatting/linting tools
• I have added tests that prove my fix/feature works
• New and existing tests pass locally
• I have updated documentation if needed
• I have reviewed the TOON specification for relevant sections

Breaking Changes

• No breaking changes
• Breaking changes (describe migration path below)

Migration path:

Additional Context

Branch: feat/serde-bridge
Intended PR order: 1-8 (this is PR 7 of 8)