fix: expose session reopen tool

[sorted-ai-bot]

Summary

• Exposes mcphub.session.open while the session is CLOSED/ARMED so AI clients can recover from session_not_open in the same MCP tool surface.
• Changes closed-session tools/call failures from the old hidden mcphub.control.open guidance to actionable call_mcphub_session_open.
• Adds unit and integration coverage for closed-session tools/list recovery, actionable failure text, and direct reopen from tools/call.

Tests

• npm install && npm run build in adapters/
• ./gradlew test --no-daemon in java/
• go test -count=1 -run TestSessionOpenRecoveryTool -v ./integration
• go test ./cmd/mcphub

Scope

• Bugfix-only public Helm patch.
• Does not sync MCPHUB internal alpha features such as capability_gap, result cache, dry-run, or task-context filtering.

[sorted-ai-bot]

@YumaKakuya PR #14 merge request