docs(kmp): fix debug-symbols Gradle syntax to match wrapped SDK version

[fishmanalex]

Summary

• docs/sdk/kmp/debug-symbols.md and the KMP Agent Skill file both instructed bugsee { ndk { enabled.set(true) } } (nested-block syntax), and the skill file additionally suggested bugseeGradle = "4+".
• Per gradle-plugin/releases.mdx, that nested-block NDK syntax and the 4.x plugin line are both new in the 4.x/SDK-7.x generation and explicitly not backward-compatible with SDK 6.x.
• KMP's own release notes (sdk/kmp/release-notes.md) say the current KMP release wraps native Android SDK 6.0.2, which requires the 3.x plugin and the old boolean form ndk(true).
• Following the instructions as written throws a Kotlin type-mismatch build error (inferred type is () -> Unit but Boolean was expected).

Changes

• Updated both files to ndk(true) and the 3.x plugin line.
• Added a note in both files pointing readers to check the KMP release notes for which native SDK generation is wrapped before picking a plugin line, since this will change as KMP tracks newer native SDK releases.

Test plan

• npx cspell on both changed files — 0 issues
• npm run build — succeeds (two unrelated pre-existing warnings on /sdk/dotnet/network/ and /sdk/xamarin/network/ are fixed by docs(dotnet,xamarin): fix raw HTML leftover breaking network.md rendering #42, not touched here)

🤖 Generated with Claude Code

https://claude.ai/code/session_01QnXDhVitCVmMNafPRvKUat

[krassx]

Validated against cross/kmp and android/gradle-plugin. The code change is right, the version guidance wasn't — I've pushed a follow-up commit (abf285f) to this branch rather than block on it.

Confirmed: ndk(true) is correct for KMP users today. Released KMP 0.1.1 (cross/kmp HEAD, 2026-05-04) wraps bugsee-android 6.0.2, and its own sample uses the boolean form:

// composeApp/build.gradle.kts @ v0.1.1
bugsee {
    appToken("...")
    ndk(true)   // upload NDK debug symbols
}

The current plugin has no Boolean overload at all — BugseePluginExtension.kt:166 only takes Action<BugseeNdkExtension> — so the previous nested-block text really was uncompilable for KMP readers.

What I changed: the bugseeGradle = "3.x.x" recommendation. That sample pairs ndk(true) with plugin 4.0.0-beta4, not 3.x, so "3.x" was an unverified pairing. And the boolean-vs-nested split turns out to be a plugin-line property rather than an SDK-line one — ndk(true) was valid on 3.x and on 4.0.0-beta4…beta9; the nested block only landed in 4.0.0-beta10 (refactor(dsl): convert ndk to a nested DSL block, 2026-05-23). So restored the neutral x.y.z placeholder and documented both syntaxes with the Type mismatch: inferred type is () -> Unit but Boolean was expected symptom, so readers can adapt rather than follow a version we haven't verified.

Heads-up on churn: cross/kmp has a large uncommitted working tree moving to bugsee-android 7.0.0-beta12 + plugin 4.0.0-beta12 + the nested DSL. This page flips back the moment that ships — the "check the release notes" framing should survive that, which is why I kept it.

Also confirmed editing docs/ai/agent-skills/sdk/kmp/SKILL.md is the right file: scripts/sync-skills.mjs treats docs/ as source of truth and generates static/, so it won't be clobbered by the prebuild hook.

cspell clean (288 files, 0 issues). LGTM to merge with the follow-up.

🤖 Generated with Claude Code

[krassx]

Validated against source (see review comment above). Approving.