docs: report Kit issues on GitHub

[danielkov]

Summary

• direct Kit agents and users to the GitHub issue tracker, with explicit user consent required before an agent submits a report
• add a bundled reporting guide covering kit --version, reproduction details, environment context, and secret redaction
• remove docs/issues after migrating its 11 active reports to Generic ACP subagents cannot fork without native session/fork #11 through Dispatched subagent errors retire the reusable session #21
• bump Kit to 0.1.90 for the bundled documentation change

Testing

• cargo test --locked docs::tests::bundled_corpus_contains_every_user_guide
• git diff --check