Add detailed roadmap issue drafts

[joelnishanth]

Motivation

• Provide ready-to-open, implementation-oriented issue specs for seven planned features to improve planning and execution.
• Reduce onboarding friction by documenting problem statements, goals, proposed designs, acceptance criteria, risks, and actionable checklists for each item.
• Target features include token-aware chunking, overlap-aware transcript splitting, benchmark harness, streaming reduce, citation/evidence spans, a SwiftUI sample app, and MLX model configuration examples.

Description

• Add seven Markdown issue drafts under issues/ named 001-token-aware-chunking.md through 007-mlx-model-configuration-examples.md each containing summary, problem, goals, proposed scope/design, acceptance criteria, risks, and suggested tasks.
• Each draft includes implementation notes such as API surface suggestions, metadata requirements, testing guidance, and task checklists to make the issues actionable.
• A repository PR record was created with the title Add detailed roadmap issue drafts summarizing the new issue files.
• No source code or public API changes were made by these additions.

Testing

• Verified the new files were written to disk and appear under the issues/ directory via local inspection, and no automated unit or CI tests were executed for this change.
• Recommend running the full test suite with swift test and the project CI to validate integration and to catch any doc-snippet or tooling regressions.

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Codex Task