Add deep-research CLAUDE.md hierarchy for Claude Code

[DavDo]

Jira issue:
https://glia.atlassian.net/browse/MOB-5174

What was solved?
Replace the legacy single .claude/CLAUDE.md with a progressive-disclosure layout: a lean root CLAUDE.md, an on-demand docs/claude-reference.md, and six subdirectory guides covering the SDK module, DI layer, chat, engagement, unified UI, and snapshot tests. Each file is grounded in actual code with verified file-path citations.

Additional info:

• Is the feature sufficiently tested? All tests fixed? Necessary unit, acceptance, snapshots added? Check that at least new public classes & methods are covered with unit tests
• Did you add logging beneficial for troubleshooting of customer issues?
• Did you add new logging? We would like the logging between platforms to be similar. Refer to Logging from Android SDKs → Things to consider for newly added logs in Confluence for more information.

Screenshots:

[snyk-io]

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