Add `gitee pr edit` for end-to-end pull request updates

[hex2dec]

Parent PRD

#2

PRD addendum comment: #2 (comment)

What to build

Implement gitee pr edit as a thin vertical slice that updates an existing pull request end-to-end through the CLI. The command should support explicit --repo or local repository inference, use the official Gitee pull request update endpoint, and return the updated pull request with the same stable text and --json contract used by pr view.

The initial slice should cover the high-frequency edit operations defined in the parent PRD addendum: updating the title, updating or clearing the body via --body or --body-file, changing state with --state open|closed, and controlling draft readiness with --draft or --ready.

Acceptance criteria

• gitee pr edit <number> supports --title, --body, --body-file, --state open|closed, --draft, and --ready, and requires at least one explicit mutation flag.
• The command preserves unspecified fields, supports --body-file - for stdin, allows an explicitly empty body to clear the remote PR body, and validates conflicting or unsupported flag combinations with stable usage errors.
• The implementation works with explicit --repo and inferred local repository context, reuses the existing authentication, canonical repository fallback, exit-code mapping, and pull-request rendering behavior, and surfaces remote validation errors clearly.
• gitee pr edit --json returns the same field contract as gitee pr view, and default text output remains readable and stable.
• Integration coverage exercises success and failure paths for title/body edits, state transitions, draft readiness changes, stdin/body-file behavior, missing authentication, repository or PR not found, and invalid argument combinations.

Blocked by

None - can start immediately.

User stories addressed

Reference from the gitee pr edit addendum on parent PRD #2:

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