release: prepare winTerm 1.3.0-beta1 prerelease

[HelloThisWorld]

Summary

Prepares the winTerm 1.3.0-beta1 prerelease — the first beta. Feature content is identical to 1.3.0-alpha4, which passed local field testing across four alpha rounds; this PR advances the channel and metadata, and rewrites the README download/feature sections.

Merging this and then pushing tag v1.3.0-beta1 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. Unlike the alphas, this beta will be listed on
winterm-site next to the stable download; WinGet still skips it.

Detailed changes

Field	alpha4	beta1
applicationVersion / tag	1.3.0-alpha4	1.3.0-beta1
packageVersion	1.3.0.3	1.3.0.4
modulePrerelease	alpha4	beta1
moduleVersion	1.3.0	1.3.0 (unchanged)
channel	alpha	beta (About metadata channel Beta)

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 the five verification scripts, with the post-bump repository sweep
grepping clean.

docs/releases/1.3.0-beta1.md covers the full Command Timeline surface, the
keyboard map, settings, the alpha-series fix history, privacy boundaries, and
the unsigned Setup EXE disclosure. Force-added because .gitignore ignores
docs/releases/*.

README now leads with the stable (Latest, v1.2.0) and beta download
channels, and the feature list gains the Command Timeline and automatic
PowerShell shell integration. verify-version.ps1 checks the README source
version against release metadata generically and separately asserts the
stable wording stays at 1.2.0, so a prerelease bump can never silently move
the recommended download.

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-beta1 / 1.3.0.4 / 1.3.0+beta1, channel beta
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 #36: Control CommandTimelineTests 44/44 on a
fresh build, including the new end-to-end Enter-keypress test). The full
Release build, installer, and packaging run in the tag-triggered release
workflow, which is the authority for them.

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
2a72171	c1fee5c	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-beta1 to trigger the release
workflow. Beta and the website download slot come after alpha4 passes local
testing.