Add tool-calling module: @Tool, ToolCallingAdvisor, returnDirect, ToolContext, and Tool Search Advisor

Every test drives the real Spring AI advisor classes (ToolCallingAdvisor,
ToolSearchToolCallingAdvisor) against a hand-written ScriptedChatModel that queues
real ChatResponse objects instead of calling a live LLM -- confirmed viable because
ChatModel has exactly one abstract method, call(Prompt) (checked with javap).

Covers:
- The plain call/execute/recall loop (WeatherTools, an ordinary @Tool method)
- @Tool(returnDirect = true) skipping the second model round trip entirely
  (ServerStatusTools)
- ToolContext: excluded from the model-facing JSON schema (verified against the
  real generated schema), still delivered to the tool from caller-supplied data
  (UserContextTools)
- A 230-tool synthetic library across six fake domains, generated via
  FunctionToolCallback.builder(...) (LargeToolLibrary)
- ToolSearchToolCallingAdvisor + RegexToolIndex: one tool ("toolSearchTool")
  offered on the first call instead of 230, with real tool-count and
  character-footprint measurements taken off the actual outgoing prompts

Findings recorded in the module's Javadoc rather than silently worked around:
- ToolCallingAdvisor only engages when the request's Prompt carries
  ToolCallingChatOptions, built from ChatModel.getOptions().mutate() (not
  getDefaultOptions(), a separate default method the request-building path never
  calls) -- confirmed by disassembling ToolCallingAdvisor.adviseCall and
  DefaultChatClientUtils
- The Tool Search Advisor's own tool is named "toolSearchTool" (camelCase), not
  "tool_search_tool" -- confirmed via @Tool(name=...) in the decompiled class
- Its session ID comes from ChatClientRequest.context() (AdvisorSpec.param), not
  from ChatClient.toolContext(Map) -- confirmed by disassembling
  ToolSearchToolCallingAdvisor.initializeSession
- RegexToolIndex matches on verb/noun substrings, not semantic relevance -- a
  real captured search for "look up an invoice" returned 5 lookup_-named tools
  across three unrelated domains alongside the one actually wanted

Co-Authored-By: Claude Sonnet 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01FtpJvZfg4nvLvtzgJTDWpB

tool-calling/output/03-tool-context-hidden-from-schema.txt

@@ -0,0 +1,16 @@
+# ToolContext: excluded from the model-facing schema, still delivered to the tool
+
+my_account input schema sent to the model:
+  {
+  "$schema" : "https://json-schema.org/draft/2020-12/schema",
+  "type" : "object",
+  "properties" : { },
+  "required" : [ ],
+  "additionalProperties" : false
+}
+
+model's tool call arguments (empty -- it was never told a userId parameter exists):
+  {}
+
+final answer, using the real userId the CALLER supplied via ChatClient.toolContext():
+  You're on the GOLD tier with a balance of $4820.50.