[Java] Tool-as-lambda 4.6: Update Java docs and ADR cross-links

[edburns]

Overview

Implement Phase 4.6 of #1810: update Java documentation for inline lambda-defined tools and ensure ADR linkage is clear.

Before coding

• Do not start any implementation work until this issue is explicitly assigned to the coding agent.
• Base branch for this work: edburns/1810-java-tool-ergonomics-tool-as-lambda.
• Read this plan file on the branch before coding:
  1810-java-tool-ergonomics-tool-as-lambda-remove-before-merge/1810-ignorance-reduction-for-implementation-plan.md

Ordering rule (important)

This issue starts only after 4.5 is merged; all Phase 4 issues are completed in listed order.

Relevant Phase 3 resolutions to apply

• 3.1 / 3.2: document the final API families and usage style.
• 3.3: document Param<T> usage and required/default behavior.
• 3.6: document fluent option modifiers on ToolDefinition.
• 3.8: keep user-facing docs aligned with final package placement and exported API.

Scope / deliverables

1. Update java/README.md with concise, accurate examples of inline lambda tool definitions.
2. Update java/docs/adr/adr-006-tool-definition-inline.md only where clarifications are needed to reflect final API names/usage.
3. Ensure examples are consistent with implemented API and behavior.

Gating criteria

• Documentation reflects final API accurately and is internally consistent.
• README includes at least one concise inline tool example.

Constraints

• Keep changes focused to Java docs directly related to this feature.
• Follow repository docs style guidance.

Completion bookkeeping

When complete, update the checkbox for Phase 4.6 in:
1810-java-tool-ergonomics-tool-as-lambda-remove-before-merge/1810-ignorance-reduction-for-implementation-plan.md