docs: clarify Forge operations and workflow configuration

[eshulman2]

Summary

• replace release-oriented control-plane guides with current operations and architecture references
• document service ownership, execution inspection, durable effects, recovery, and operator access
• expand workflow management and declarative customization guidance while separating project configuration from trusted core extensions

Verification

• Zensical documentation build passed.
• The full pytest suite was attempted, but the existing E2E test tests/e2e/test_feature_workflow_e2e.py::test_feature_workflow_routes_generates_and_pauses timed out before an assertion. The timeout also reproduced when this worktree source was explicitly selected through PYTHONPATH.

This PR is documentation-only.