cargo: release 0.20.1

[fosskar]

Bumps [workspace.package] version to 0.20.1. That is the entire release: nix/effects.nix tags v0.20.1 and creates the GitHub release with --generate-notes once nixbot goes green on main. No hand tagging.

Why PATCH

Three changes landed since v0.20.0, all internal — no features, nothing breaking:

PR	Change
#71	cli: single-source the systemd hardening set
#72	core: give the pass verdict one definition
#73	core: give the encrypted session store one owner

Per the pre-1.0 rule (feature/breaking → MINOR, bugfix/internal → PATCH), this is a PATCH.

#71 is the only one that changes a shipped artifact: the unit written by ssync service install now lists the sandbox properties alphabetically, because all three renderers derive them from one TOML table. The property set is unchanged — verified by diffing the rendered set against the pre-change constant, 28 lines in and 28 out — and systemd is order-insensitive here, so behaviour is identical. Anyone diffing an existing unit file will see the reordering.

#72 and #73 are internal to ssync-core with no observable behaviour change.

Verification

• Cargo.toml is the only place carrying the version; nix/package.nix and nix/effects.nix both read it via lib.importTOML, and nix eval .#default.version now resolves 0.20.1
• cargo check --workspace ran, so Cargo.lock is updated — all five workspace crates now 0.20.1, committed alongside
• cargo clippy --workspace --all-targets -- -D warnings — clean
• cargo test --workspace -- --test-threads=1 — 260 passed, 0 failed
• nix fmt -- --ci — 0 changed

Note on the generated notes

--generate-notes lists merged PRs between tags, so #71/#72/#73 and this bump will appear. Nothing was pushed directly to main, so nothing is missing from the notes.