docs(admin-cli): document --forced, --sort, --diagnostics, and --force flags in README #886

Problem

The command synopsis and subcommand documentation in crates/apps/admin/cli/README.md predate several flags in crates/apps/admin/cli/src/cli.rs:

• drain-node <node> (cli.rs:30-89) accepts --forced and --no-replace-after-terminate, which are absent from README.md:12.
• list-nodes (cli.rs:195-239) accepts --sort <name|drainability> (which requires --role), --long-runner-age-hours <N>, and -v / --verbose, which are absent from README.md:15.
• get-node <node> (cli.rs:107-116) accepts --diagnostics, which is absent from README.md:16.
• template build (cli.rs:152-165) accepts --force, which is absent from README.md:9-10.

Why it matters

crates/apps/admin/cli/README.md is published as the Operator CLI chapter of the hosted SPACE guide (docs/book/SUMMARY.md). Operators consulting the guide cannot see that space-admin-cli supports forced drains, ASG capacity-decrement drains, drainability ranking, or per-node residency diagnostics without reading the Rust source or --help.

Proposed approach

Update the synopsis block and relevant sections in crates/apps/admin/cli/README.md to match the flags defined in crates/apps/admin/cli/src/cli.rs.

Severity

Low / does not apply (documentation-only sync with existing CLI flags).