Release v1.3.0

Promote `[Unreleased]` to `[1.3.0]` with today's date. The section
covers stash support, four New Diff dialog optimizations, and two
bug fixes shipped on master since v1.2.0:

Added:
- Stash support in the ref-picker popup plus a dedicated "View stash"
  mode in the New Diff dialog (#7).
- New Diff dialog auto-detects a GitHub PR URL on the clipboard.
- New Diff dialog: *Branch vs merge-base* auto-seeds the partner
  field with `origin/<default-branch>`.
- New Diff dialog: cold-launch seeds the repo path from the most
  recent diff in the MRU.

Fixed:
- Annotated tags now resolve everywhere a commit-ish is accepted
  (ref-picker, validator, diff enumeration, CLI). LibGit2Sharp's
  generic `Lookup<Commit>` returns null for the TagAnnotation
  wrapper; resolution is now consolidated in
  `CommitIshResolver.PeelToCommit` and shared across all paths.
- New Diff dialog `Pick...` buttons enable as soon as the repo path
  resolves, rather than waiting for a commit-ish to be typed.

Minor bump per AGENTS.md §12 since the set is feature-led.

AI-Local-Session: 57980504-219e-4635-b420-38b328af9e61
AI-Cloud-Session: 46e3fd4c-04e1-4362-891d-c97594821d9d
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: geevensingh

CHANGELOG.md

@@ -12,6 +12,8 @@ body. Keep section headings exact and write notes in Markdown.
 
 ## [Unreleased]
 
+## [1.3.0] - 2026-05-20
+
 ### Added
 
 - **Stash support in the ref-picker popup.** The "Pick…" popup next