build: add a lint guard for inline fully-qualified names (custom detekt rule)

[rustyrazorblade]

Follow-up from #794 (merged). That PR removed ~28 inline fully-qualified type names in favor of imports, but no lint rule prevents recurrence.

Finding

There is no built-in detekt 1.23.8 or ktlint rule that flags an inline FQN used where an import would do. A real guard needs a custom detekt ruleset module (jar + RuleSetProvider + META-INF/services), wired type-resolution-aware against the existing detektMain/detektTest/detektIntegrationTest tasks so it can distinguish a genuine same-name collision (which must stay FQN'd) from a shortenable FQN — plus its own tests and a baseline for the legitimate collision cases.

Legitimate FQNs that a rule must NOT flag (from #794)

• project DockerException vs dockerjava DockerException (Docker.kt, RetryUtil.kt, ContainerExecutor.kt, ContainerExecutorTest.kt)
• fabric8 Container vs testcontainers Container (K8sServiceIntegrationTest.kt)
• java.lang.Long/Double/Float/Boolean::class.java (McpToolRegistry.kt)
• ResultCallback.Adapter<Frame> (DockerTest.kt — owned by build: treat Kotlin compiler warnings as errors (and fix the fallout) #780)

Recommendation

Worthwhile only if the pattern recurs. If it does, build the custom rule as above. Low priority until then.