feat: add Obsidian opener and per-opener filter metadata (0.2.0)

[sksizer]

Summary

• Adds an Obsidian opener that builds obsidian:// URIs by reading the user's own obsidian.json to discover registered vaults and routing the path through a three-way strategy ladder (vault root → ?vault=Name; file inside a vault → ?vault=Name&file=rel; outside any known vault → ?path=abs). All Obsidian/URI specifics stay inside src/obsidian.rs — no Vault or URI scheme leaks to the public API.
• Adds per-opener filter metadata so consumers can build "what can I open this with?" UIs: accepts_directories: bool plus a concrete enum FileSupport { Any, NotSupported, Extensions(Vec<String>) }. Every built-in declares both fields explicitly via macro-required arguments — no silent defaults.
• Adds an open(path: &Path, app_id: &str) convenience that resolves the opener from the registry internally. Legacy open_path(command, path) from 0.1.x is retained as a primitive. Existing open_with(opener, path) stays as the lower-level entry point.

Bump to 0.2.0 (minor — PathOpener field shape changed). Fixes the Cargo.toml repository/homepage URLs that pointed to a non-existent rs-path-opener repo.

Task

Tracked in the consuming project at docs/planning/tasks/2026-05-16-path-opener-uri-scheme-and-obsidian.md (in sksizer/polish). That document carries the full Goal / Today / Proposed / Approach / ACs / Out-of-scope / Discovery-context, including the design pivot away from a public LaunchStrategy/TargetKind enum.

Acceptance criteria

• AC-1: Public API is exactly open, open_default, open_with, open_path (legacy primitive retained per user call), detect_installed_apps, PathOpener, FileSupport. No LaunchStrategy, no TargetKind. grep "[Vv]ault" src/lib.rs returns only one hit, an internal // (not ///) comment inside the private Launch enum — not rendered in docs. pub(crate) mod obsidian and pub(crate) struct Vault keep that vocabulary crate-private.
• AC-2: enum FileSupport { Any, NotSupported, Extensions(Vec<String>) } derives specta::Type under the specta feature. Variant name stayed Extensions; Vec<String> reshape (vs &'static [&'static str]) was the spec's Approach-8 escape-hatch (b) — forced by serde Deserialize on PathOpener. Private FileSupportSpec sibling carries the &'static form so the const KNOWN_APPS table doesn't allocate; conversion happens at detect_installed_apps() time. README migration notes document.
• AC-3: Every built-in declares both metadata fields, enforced at the macro signature. Audit test every_known_app_declares_expected_metadata walks the registry. Editors / file-managers → (true, Any); terminals → (true, NotSupported); Obsidian → (true, Extensions(["md","markdown","canvas"])).
• AC-4: Obsidian registered with Launch::Custom(obsidian::build_command). macOS detection via MacAppBundle("Obsidian.app"). Linux/Windows use new Detection::AlwaysUnavailable variant so they always report is_available: false (avoids false-positive on any unrelated obsidian binary on PATH) with TODO pointing to the follow-up.
• AC-5: uri_for_vault_root_uses_vault_query_only — ?vault=<Name>.
• AC-6: uri_for_file_inside_vault_uses_vault_and_file — ?vault=<Name>&file=<rel>.
• AC-7: uri_for_path_outside_any_vault_falls_through_to_path_query — ?path=<abs>.
• AC-8: parse_handles_missing_unreadable_malformed_inputs covers the JSON-parse error branch; discover_does_not_panic covers the runtime path; missing-file / unreadable-bytes branches are simple let Ok(..) = .. else { return Vec::new() }.
• AC-9: 5 doctests pass under cargo test --doc, including the README's openers_for(path) example that filters by both accepts_directories and file_support. README is include_str!'d into src/lib.rs so its examples are exercised.
• AC-10: cargo test (16 unit + 5 doc) green; cargo check --all-features green.
• AC-11: Cargo.toml repository and homepage corrected to https://github.com/sksizer/rust-path-opener.
• AC-12: 0.2.0 published on crates.io + v0.2.0 tag — not yet. Cargo.toml bumped, tree clean; to be done by maintainer after merge via cargo publish + git tag v0.2.0 && git push --tags.

Test plan

• Pull the branch, just ci runs green locally.
• On macOS with Obsidian installed and at least one registered vault: open(vault_root, "obsidian") opens Obsidian to that vault; open(vault/sub/file.md, "obsidian") opens the note. Unregistered path still launches Obsidian (it'll prompt).
• detect_installed_apps() filtered by accepts_directories: true + file_support: Extensions("md") matches md files to Obsidian + any general editors (VS Code, Zed, ...), excludes terminals.
• Review the README rewrite for tone / examples / migration-notes clarity.