feat: add copy-archive global action

[backnotprop]

Adds a global copy-archive action next to copy-context, so the "hand annotations to the agent, then clear the list" step can be bound to one Herdr key instead of prefix+m then C.

What changed

• Bun runtime: src/export-archive.ts mirrors export.ts and calls copyAndArchiveAnnotations with the same dependencies the manager passes. Outcomes map to notifications: archived (exit 0), nothing to copy (exit 0, same wording as copy-context), clipboard or store failure (exit 1). Archived sets remain restorable from the manager.
• Rust Lite runtime: copy-archive subcommand in rust/src/cli.rs with the same wiring and messages; lite-rs/herdr-plugin.toml gains the action.
• Manifests: the action is added after copy-context in herdr-plugin.toml, lite/herdr-plugin.toml, and lite-rs/herdr-plugin.toml. No existing id, command, key, or platform gate changed.
• Parity: four process.copy-archive.* cases in scripts/parity-lite.py (empty, populated with store bytes compared, clipboard failure, missing state), plus a verify_manifests() step that compares action and pane declarations across the three manifests and asserts every entrypoint is driven. docs/rust-lite-parity-proof.md and docs/rust-lite-parity.md updated. rust-lite-ci now also runs on src/**, lite/**, and herdr-plugin.toml changes since the harness reads them.
• Docs: README key table and suggested [[keys.command]] binding (prefix+ctrl+a).
• Smoke suites expect the new action.

Validation

• bun test 73 pass, bunx tsc --noEmit clean
• cargo fmt --check, cargo clippy --all-targets -D warnings, cargo test 56 lib + 4 integration pass
• scripts/parity-lite.sh: 459 observables, 92 screens, zero divergences / 1 deliberate
• Live, in a disposable Herdr session on 0.8.2, for both the Bun manifest and the staged Rust Lite manifest: action listed; empty store reports "No annotations" and exits 0; a seeded store of two annotations produces Markdown on the clipboard, an empty active list, and one new archive set containing both ids. scripts/smoke-rust-lite.sh: 0 failures.

refs #36