fix(release): use cargo-workspace + linked-versions plugins

[non7top]

Fixes the run that failed after #37 merged: https://github.com/non7top/sort4print/actions/runs/36226824050 — release-please failed: is not a package manifest (might be a cargo workspace).

What happened

#37 fixed the first crash (each member now has a literal version, not version.workspace = true), and the next run got further — it correctly walked and updated all four members. But it then also tried to treat the root Cargo.toml as a package manifest (since our config had a single "." package entry with release-type: "rust"), and our root is a pure virtual manifest (only [workspace], no [package] section) — so that check failed.

The fix

Checked release-please's actual plugin source (src/plugins/cargo-workspace.ts, src/plugins/linked-versions.ts) and a real working example, google/rust_icu's release-please-config.json. For a pure virtual workspace root, the right shape is:

• One "packages" entry per member directory (core, app, tools/pack-cities, tools/pack-flags), not a single "." entry.
• The cargo-workspace plugin, which understands a virtual root and manages the shared Cargo.lock.
• The linked-versions plugin with merge: true, which keeps all four releasing together as one PR/tag — matching what the shared version.workspace = true gave us before this whole detour started.

.release-please-manifest.json is now keyed by member path to match.

One behavior change worth flagging: no changelog-path override this time, so (confirmed against rust_icu's actual repo layout) each member gets its own CHANGELOG.md in its own directory, rather than one shared root file. Went with the default rather than guess at changelog-path's path-resolution rules to force a shared file.

Builds on #37 (merged).

[github-actions]

Windows build ready for 74b47c8 (17.3 MB):

• sort4print-74b47c8.exe

Download and run it. No unpacking, no installer, no runtime needed.

[non7top]

Addressed non7top/release-please-forecast#20, which this PR's switch to the cargo-workspace/linked-versions plugins (no "." manifest key) exposed:

• release-please-forecast (Fix crop-margin dim wash bleeding into the picked-photo surround #20's manifest-key bug + changelog-repeat bug): fixed in fix: stop hardcoding manifest's "." key; dedupe linked-versions changelog repeats release-please-forecast#21, released as v1.5.1. Adds a package-name input and defensively collapses the repeated <details> blocks seen in the earlier preview comment.
• gh-workflows: release-please-preview.yml had no way to pass package-name through to the action — feat: pass a package-name input through to release-please-forecast gh-workflows#1 threads it.
• This PR: bb7d259 sets package-name: core explicitly, so the preview stops guessing (correctly, but silently) from the manifest's first key and states it instead — see the preflight-warning comment.

The package-name: core line won't take effect until gh-workflows#1 merges (it's still pointed at @main), so the next preview run here will keep warning until then.

[github-actions]

Windows build ready for 81b0c60 (17.3 MB):

• sort4print-81b0c60.exe

Download and run it. No unpacking, no installer, no runtime needed.

[github-actions]

🤖 release-please PREVIEW

What merging this PR into master would trigger:

🤖 I will create a release beep boop

0.5.0

0.5.0 (2026-09-26)

Bug Fixes

• release: give each crate a literal version instead of workspace-inherited (bbe21e3)
• release: give each crate a literal version instead of workspace-inherited (ceab4bc)
• release: leave the literal versions at 0.1.0, not 0.5.0 (3ef4898)
• release: use cargo-workspace + linked-versions plugins (the merge commit GitHub would create for this PR)

Miscellaneous Chores

• release 0.5.0 (db52758)

---

This PR was generated with Release Please. See documentation.

_{Two entries, one change: release-please reads both the commit on this branch and the merge commit GitHub will create, whose body is this PR title. Both really do land in the published changelog. Only the merge commit has no SHA to cite, because it does not exist yet.}

_{Predicted from bb7d259 merged into master at bbe21e3, with the PR title read as fix(release): use cargo-workspace + linked-versions plugins · Full run}