check lokalize generated translation sources into the tree

[VishnuSanal]

Fixes #1811

• Tests pass
• Appropriate changes to README are included in PR

Translation sources rendered by the lokalize plugin from values*/strings.json
are now checked into the tree instead of generated into build/ on every
compile. This fixes two things:

1. Non-Gradle downstreams can compile the source tree as-is. Previously the
   generated Kotlin (GeneratedTranslations, Strings_*, GeneratedStringKeys)
   only existed after a Gradle build, so a plain source checkout didn't compile.
2. Removes the configuration-time build lag: the old
   configureEach block realized every task in the project just to wire the
   generator onto the compile path. With generation off the compile path, it's
   gone.

What changed

Checked-in modules (multipaz-doctypes, multipaz-utopia)

• Rendered Kotlin is committed under src/commonMain/generated/.
• generateMultipazStrings writes there on demand (run it after editing strings); compiling no longer regenerates.
• lokalizeCheckGenerated renders in memory and fails the build if the committed sources drift from strings.json, printing the exact regen command. It's wired into check, so ./gradlew build enforces it — including CI (unit-test.yml runs build).

Plugin

• Legacy build/-generation mode and its configureEach block deleted (zero users remain once both JSON modules are checked in).
• generatedSourceDir demoted from a mode toggle to a convention-defaulted override (src/commonMain/generated).
• outputDir routes XML modules to a throwaway build/ path so a skipped run never touches src/.

multipaz-compose (unchanged behavior)

• It's an XML module — strings resolve via Compose Resources at runtime, no Kotlin is generated, so generateMultipazStrings skips.
• Removed the dead androidReleaseSourcesJar dependsOn generateMultipazStrings hack.

.gitattributes

• Marks */src/commonMain/generated/** linguist-generated=true so it collapses in diffs and signals it's never hand-edited.

How the safety net works

strings.json (source of truth, committed) → generateMultipazStrings → src/commonMain/generated/*.kt (committed). lokalizeCheckGenerated (in check) guarantees the two never diverge on a merged PR.

Testing

• ./gradlew :multipaz-doctypes:lokalizeCheckGenerated :multipaz-utopia:lokalizeCheckGenerated
  — both pass (✓ Generated strings are up to date (23 languages)).
• Editing a strings.json makes the drift check fail with the fix command; regenerating restores green.
• Clean from-scratch builds of all three modules (build/ wiped); KSP (kspCommonMainKotlinMetadata) and jvmTest pass; build/generated/kmp never reappears for the JSON modules.
• Dry-run task graphs confirm generateMultipazStrings is off every compile and sourcesJar path.
• multipaz-compose source tree stays pristine — the skipped generator writes nothing under src/.

[hanluOMH]

Looks good to me