chore(release): prepare 0.7.0

Bump the workspace and internal crate pins to 0.7.0 so the next
minor release can be published from a single coherent repo state.
This also updates the in-repo release-facing references that still
pointed at 0.6.0 and reruns the documented local release checklist.

Constraint: Release prep must keep the workspace version, internal crate pins, and release-path assertions in sync
Constraint: cargo publish --dry-run checks Git dirtiness even when jj already records the mutable change state
Rejected: Fold in extra code cleanups during the release cut | would broaden a release-only change without improving publishability
Confidence: high
Scope-risk: narrow
Reversibility: clean
Directive: When running release dry-runs from an active jj working-copy change, export first or use --allow-dirty
Tested: cargo test
Tested: cargo build -p taskers --bin taskers --bin taskers-gtk
Tested: env TASKERS_TERMINAL_BACKEND=mock bash scripts/headless-smoke.sh ./target/debug/taskers --smoke-script baseline --diagnostic-log stderr --quit-after-ms 5000
Tested: bash scripts/smoke_linux_release_launcher.sh
Tested: cargo publish --dry-run --allow-dirty -p taskers-domain
Tested: cargo publish --dry-run --allow-dirty -p taskers-paths
Tested: cargo run -p taskers-cli -- --help
Tested: cargo run -p taskers-cli -- notify --help
Tested: cargo check
Tested: cargo clippy --workspace --all-targets
Tested: cargo install --path crates/taskers-app --force
Not-tested: pushing tag v0.7.0 to origin and publishing the draft GitHub release/assets
Not-tested: full crates.io publish sequence for the dependent workspace crates

chore(publish): enable crates.io publishing for host, shell, and shel…

…l-core

These three crates were added after the 0.3.x release cycle with
publish = false while their APIs stabilized. They are now required
transitive dependencies of the published taskers app crate, so they
must be publishable for cargo install to resolve correctly.

Also adds taskers-core, taskers-shell-core, taskers-host, and
taskers-shell to the documented publish order in docs/release.md.

Constraint: crates.io requires all non-optional path deps to be published
Confidence: high
Scope-risk: narrow
Tested: cargo publish --dry-run -p taskers-domain, taskers-paths (leaf crates)
Not-tested: full sequential publish of all 11 crates

chore(release): bump workspace version to 0.3.1

fix: build universal macOS release assets

chore: release v0.2.1

chore: release v0.2.0