release: prepare winTerm 1.3.0-alpha3 prerelease

[HelloThisWorld]

Summary

Prepares the winTerm 1.3.0-alpha3 prerelease. The five alpha2 field-report
fixes are already on main through #34; this PR only moves the release
metadata.

Merging this and then pushing tag v1.3.0-alpha3 will run the full release
workflow and publish a GitHub prerelease with Setup EXE and Portable ZIP.

Latest is protected. The release workflow marks any channel other than
stable with --prerelease --latest=false, so /releases/latest keeps
resolving to v1.2.0. This alpha is deliberately not listed on
winterm-site and not submitted to WinGet.

Detailed changes

Field	alpha2	alpha3
applicationVersion / tag	1.3.0-alpha2	1.3.0-alpha3
packageVersion	1.3.0.1	1.3.0.2
modulePrerelease	alpha2	alpha3
moduleVersion	1.3.0	1.3.0 (unchanged)
channel	alpha	alpha (unchanged)

Surfaces moved together: version.json, shell/shared/version.json,
ReleaseMetadata.h, MSIX manifest, the three .rc scripts, the module
manifest, the workspace serializer fallbacks, and the version literals pinned
by verify-version.ps1, verify-branding.ps1, test-visual-progress.ps1,
test.ps1, and package-shell-assets.ps1 (this pass used a sweep that greps
the repository clean of the previous version literals before the gates run).

docs/releases/1.3.0-alpha3.md documents the five fixes in a "Changes since
alpha2" section plus the antivirus resilience note and the unsigned Setup EXE
disclosure. Force-added because .gitignore ignores docs/releases/*.

Validation performed

Environment: Windows 11 Pro 26100, MSVC 14.44.35207, Windows SDK 10.0.26100.0.

Repository scripts — ran, passed

Command	Result
verify-version.ps1	PASS — 1.3.0-alpha3 / 1.3.0.2 / 1.3.0+alpha3, channel alpha
verify-branding.ps1 -ExpectedPublisher 'CN=helloThisWorld'	PASS
test-release-workflow.ps1	PASS
test-ci-classification.ps1	PASS
test-command-timeline.ps1	PASS
test-visual-progress.ps1	PASS
test-privacy.ps1	PASS
test.ps1 -Suite Smoke -Configuration Release -Platform x64	PASS

Static — git diff --check clean.

Not run, with reason — compiled tests: no source change in this PR (the
fixes were built and tested in #34: SettingsModel winTerm classes 44/44,
Control CommandTimelineTests 43/43 on fresh builds). The full Release build,
installer, and packaging run in the tag-triggered release workflow, which is
the authority for them. test-shell-integration.ps1 -Shell All remains
blocked locally by antivirus on Compatibility.ps1; it runs in the release
workflow's gates.

No screenshot was needed or created. winterm-site is untouched.

Checklist

• The change is focused and does not include unrelated formatting.
• Tests were added or updated where appropriate.
• All tests claimed above actually ran and passed.
• User-facing behavior and limitations are documented in this repository.
• This source/docs commit updates the root CHANGELOG.md.
• The Wiki Development-Changes.md ledger has been pushed with the final source SHA, link, summary, and checkpoint/release.
• Documentation screenshots reuse a suitable existing sanitized winterm-site asset, or no screenshot was added.
• Version or schema changes include compatibility and migration notes.
• Package identity, winterm.exe, and Microsoft Terminal coexistence remain isolated.
• No command text, terminal output, clipboard content, credentials, or private paths are logged.
• New source and script files contain the appropriate MIT license header.
• I did not include generated build output, secrets, certificates, or local absolute paths.

Source ↔ Wiki mapping

Source commit	Wiki commit	Wiki pages
9f8198c	cf9af5c	Development-Changes, Changelog

Boundary

Workspace schema (2), docking model (1), shell protocol (1), theme schema (1),
update manifest schema (1), package identity, and signing policy are unchanged.
No feature code changes. No winterm-site change. No WinGet submission. Latest
stays v1.2.0.

Next step after this merges: push tag v1.3.0-alpha3 to trigger the release
workflow. Beta and the website download slot come after alpha3 passes local
testing.