Enforce manifest command trust before project command execution

[codeforester]

Follow-up to #1367 and #1381

After manifest command trust records and basectl trust commands exist, wire enforcement into the command paths that execute project-owned manifest code.

Scope

• Block basectl test [project] before execution when no matching allow record exists.
• Block basectl run <project> <command> before execution when no matching allow record exists.
• Block basectl build <project> [target...] before execution when no matching allow record exists.
• Block basectl demo [project] before running manifest-declared demo scripts when no matching allow record exists.
• Block basectl activate <project> before sourcing activate.source entries when no matching allow record exists.
• Preserve read-only inspection paths: --dry-run, --list, projects list, workspace status/check/doctor, check, doctor, and export-context.
• Print the blocked-command text from docs/manifest-command-trust.md, including review commands and the exact basectl trust allow ... --manifest-sha256 ... command.

Acceptance Criteria

• BATS cover blocked execution for test/run/build/demo and activation source paths.
• BATS cover that dry-run/list/read-only paths still work before approval.
• Non-interactive shells fail closed without prompting.
• Docs include the CI allow-step example once enforcement lands.