docs: add CloudShell FOG integration profile (current-main draft)

[mdheller]

Summary

Adds the TurtleTerm-side CloudShell FOG integration profile and receipt-context smoke test on a fresh branch from current main.

Why this replaces PR #3

The earlier PR #3 branch diverged heavily from main while upstream added TurtleTerm CloudFog, Superconscious, and Agent Machine bridge surfaces. This replacement branch starts from current main and replays only the integration artifacts plus the minimal current-main-safe fixes proven by CI triage.

Included

• docs/integration/cloudshell-fog.md
• assets/sourceos/tests/test_cloudshell_fog_receipt_context.py
• sibling-path resolution for bridge wrappers that invoke turtle-agentctl
• generated RPM builder fix so %install invokes the staging helper through bash

Integration scope

This PR documents and validates:

• CloudShell FOG session/audit correlation
• TurtleTerm ownership of terminal receipt semantics
• SOURCEOS_* environment propagation from CloudShell context
• receipt context preservation for session, workspace, actor, policy bundle, and execution domain

Follow-up tracking

Remaining repo-wide checks should stay tracked separately if they still fail:

• native Linux package verification: Stabilize native package build verification for RPM/Debian/Arch #7
• cargo-audit posture: Classify and remediate cargo-audit findings #8
• Homebrew install-from-HEAD validation: Stabilize Homebrew install-from-HEAD validation #9