chore: release 1.2.0

[mortenboye]

Versions all eight packages at 1.2.0 with changelogs. Prepared on top of master at c90f5de; #168 is deliberately not included and will land in the next release.

What's in it

• addVirtualDevice, removeVirtualDevice and setNetworkSessionEnabled return Future<void> (addVirtualDevice drops its Future, so errors surface as unhandled exceptions #173 → fix: return futures from virtual device and network session APIs #174). The platform call was previously discarded, so failures escaped as unhandled asynchronous errors that no try/catch at the call site could see.
• iOS no longer shows the local-network permission prompt at app startup (fix(darwin): create MIDINetworkSession lazily, not at plugin init #175, thanks @aleksei-svezhevskii). The MIDI network session is created on the first setNetworkSessionEnabled(true) instead of at plugin init.
• CI-only work from ci(darwin): compile the plugin and run its Swift tests #176 and ci: check formatting, publishability and the example's tests #177 (darwin compile + Swift tests, format/publish/example checks) — no user-facing change, so it appears only as the version bump in the packages it touched.

Why minor, not patch

The three signature changes are source-compatible for callers that ignore the result, but anyone implementing MidiCommandPlatform must widen those overrides from void. That is more than a patch communicates, so 1.1.2 → 1.2.0.

Also fixed here: a publish blocker

While verifying, publish:dry-run measured the darwin package at 273 MB instead of 18 KB. Its .pubignore still excluded the pre-federation ios/.build/ path, so the Swift build output that tool/darwin_native_checks.sh now produces was being packaged. pub.dev's limit is 100 MB, so a publish from any machine that had run the darwin checks would have failed — including the local publish flow this repo uses. The .gitignore entries added in #176 do not help, because a parent .gitignore does not apply to a package in a subdirectory; the paths have to be in .pubignore. Verified: with 252 MB of .build present, the archive is back to 19 KB.

Verification

On the committed release branch: melos bootstrap (9 packages), format:check, analyze, analyze:example, test (6 packages), test:web:chrome, tool/darwin_native_checks.sh (5 Swift tests) and publish:dry-run all pass — the last reporting 0 warnings for all eight packages.

Before publishing

• There is no v1.1.2 tag — the tag series stops at v1.1.1, so 1.1.2 shipped untagged. Worth creating it retroactively at e1e988c alongside v1.2.0, otherwise any future melos version run computes its commit range from v1.1.1.
• Publish order still matters, since the ^1.2.0 constraints are not on pub.dev yet: flutter_midi_command_platform_interface first, then the six implementation packages, then flutter_midi_command.