[core][doc] Refactor parse-related functions by adding new shared helpers and a unified parse loop + Add a document on parsing algorithm

[forfudan]

This PR refactors Command parsing to reduce duplication by extracting a shared lexing/dispatch loop and common storage helpers, aiming to keep parse_arguments() and parse_known_arguments() aligned.

Changes:

• Replaces the inline parse loop in parse_arguments() with a shared _run_parse_loop(...).
• Updates parse_known_arguments() to use _run_parse_loop(...) and limits its post-parse phases (no prompting/confirmation).
• Extracts repeated parsing/storage logic into helpers (_store_scalar_value, _increment_count, _consume_nargs, _find_remainder_slot).

[Copilot]

Pull request overview

Refactors Command parsing to reduce duplication by extracting a shared lexing/dispatch loop and common storage helpers, aiming to keep parse_arguments() and parse_known_arguments() aligned.

Changes:

• Replaces the inline parse loop in parse_arguments() with a shared _run_parse_loop(...).
• Updates parse_known_arguments() to use _run_parse_loop(...) and limits its post-parse phases (no prompting/confirmation).
• Extracts repeated parsing/storage logic into helpers (_store_scalar_value, _increment_count, _consume_nargs, _find_remainder_slot).

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.