docs: align estate and memory contracts with current code

[rldyourmnd]

Changes

• Correct the public example estate documentation to match its five owners, seven selectors, actual managed selectors, and absence of archived selectors.
• Correct the architecture binary count and remove a nonexistent version ledger link.
• Document the implemented read-only gds memory generate and gds memory verify flow, and the public anchor's disabled Serena memory state.

Verification

• go test ./core/estate ./core/memory
• gds --cwd /tmp/gds-doc-audit-20260929/github-device-sync validate estate --json (succeeded)
• Local Markdown link/path audit