feat: add agents.conversations.* methods

[zimeg]

Summary

Adds the 9 Slack Code / code channel Web API methods to the Java Web API client, extending the existing agents.* namespace (agents.sessions.* already ships). All 9 require the bot scope code_channels:manage.

Method	Rate limit	Notes
agents.conversations.create	t2	Create a dedicated code channel for an agent session
agents.conversations.archive	t2	Archive a code channel
agents.conversations.setProperties	t3	Set properties on a code channel
agents.conversations.setView	t3	Create or update a view in a code channel
agents.conversations.setCommands	t1	Register the agent's slash commands for a code channel
agents.conversations.listViews	t3	List the views attached to a code channel
agents.conversations.removeView	t3	Remove a view from a code channel
agents.conversations.getCanvas	t3	Fetch a canvas attached to a code channel
agents.conversations.setCanvasContent	t3	Replace the full markdown content of a plan canvas

Notes

• Experimental / draft. Slack Code (code channels) is in a developer-GA state; the API and its docs are still landing (docs PR Unable to connect to RTM Api using java-slack-sdk #816). This PR is a draft pending API + docs stabilization. Request/response shapes may change before GA.
• Arg-name caveat preserved. getCanvas and setCanvasContent take the channel argument (modeled as the channel field); the other 7 take channel_id (modeled as channelId).
• No legacy codeChannels.* names are added (per the 2026-09-23 decision to ship agents.conversations.* only).
• Honest, minimal shapes. Undocumented complex/object args (code_channel, agent_resource, csp, commands) are exposed as JSON-encoded String params (the *AsString pattern, mirroring blocks.validate) rather than guessing nested models; setView additionally accepts a typed List<LayoutBlock> for blocks. Response classes carry only the common top-level fields (ok/error/warning/needed/provided) because the API reference does not yet document response bodies.

Files

18 new request/response classes under com.slack.api.methods.{request,response}.agents.conversations, plus wiring in MethodsClient / MethodsClientImpl, AsyncMethodsClient / AsyncMethodsClientImpl, RequestFormBuilder, the Methods constants, and MethodsRateLimits.

Testing

• mvn -pl slack-api-client -am compile — BUILD SUCCESS
• mvn -pl slack-api-client -am test-compile — BUILD SUCCESS
• MethodsTest (endpoint coverage) + MethodsRateLimitsTest — green (3 tests, 0 failures)
• Remote API integration tests were not run (require live Slack credentials).

🤖 Generated with Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 8.33333% with 99 lines in your changes missing coverage. Please review.
✅ Project coverage is 72.31%. Comparing base (49b62a6) to head (a9f095b).
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
...java/com/slack/api/methods/RequestFormBuilder.java	0.00%	63 Missing ⚠️
...slack/api/methods/impl/AsyncMethodsClientImpl.java	0.00%	18 Missing ⚠️
.../com/slack/api/methods/impl/MethodsClientImpl.java	0.00%	18 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #1647      +/-   ##
============================================
- Coverage     72.79%   72.31%   -0.48%     
  Complexity     4550     4550              
============================================
  Files           483      483              
  Lines         14456    14564     +108     
  Branches       1513     1516       +3     
============================================
+ Hits          10523    10532       +9     
- Misses         3038     3137      +99     
  Partials        895      895              

Flag	Coverage Δ
jdk-14	72.31% <8.33%> (-0.48%)	⬇️

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