Support resuming AI sessions from a selected UUID

[Copilot]

Resume now recognizes a selected UUID in the current buffer and seeds the resume args prompt with it, matching the existing C-u R flow without requiring a prefix arg. This makes it faster to reopen a known prior session directly from copied/session-linked IDs.

• Resume arg resolution

  • Taught the shared backend start-command resolver to detect an active region containing a UUID in 8-4-4-4-12 form.
  • Limited the behavior to resume commands only (resume / --resume).
  • When a UUID is selected, resume prompts for args and appends the session id after the existing resume switches.

• Behavioral guardrails

  • Non-UUID selections continue to behave exactly as before.
  • Existing explicit-prefix resume behavior remains unchanged.

• Targeted ERT coverage

  • Added tests for:
    • --resume flows prefilled with the selected UUID
    • resume subcommand flows prefilled with the selected UUID
    • non-UUID selections being ignored

Example:

;; Buffer selection:
123e4567-e89b-12d3-a456-426614174000

;; Invoke resume without C-u:
M-x ai-code-cli-resume

;; Prompt is prefilled like:
--resume 123e4567-e89b-12d3-a456-426614174000

[Copilot]

Pull request overview

This PR improves the CLI resume UX across backends by detecting a selected UUID in the active region and using it to prefill the resume-args prompt (without requiring a prefix argument), aligning the flow with the existing interactive C-u resume behavior.

Changes:

• Added UUID-shaped region detection (8-4-4-4-12) and used it to trigger/seed prompting for resume commands only (resume / --resume).
• Updated shared start-command resolution so selected UUIDs are appended to the default args and included in the resolved command/args plist.
• Added targeted ERT coverage for --resume, resume subcommand, and non-UUID selections.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
ai-code-backends-infra.el	Adds UUID detection from the active region and extends command resolution to prefill resume args when a UUID is selected.
test/test_ai-code-backends-infra.el	Adds ERT tests validating UUID-prefill behavior for both --resume and resume flows, and ensuring non-UUID selections are ignored.

[tninja]

@copilot we can trim the leading and trimming space from the selected region, and then do UUID detection.

[Copilot]

@copilot we can trim the leading and trimming space from the selected region, and then do UUID detection.

Already covered in 7b19659: ai-code-backends-infra--selected-session-id trims the selected region with string-trim before running UUID detection, so leading and trailing whitespace are ignored.