feat: add contextual actions across Harbor

[OwaisByte]

Summary

Right-clicking a Harbor poster currently opens different menus depending on which component rendered it. Collections, downloads, profile content and nested links/images can instead fall through to WebView page commands, while file and membership actions need different targets and guarantees.

This adds a shared context-action system that composes the registered entity, its explicit membership/page context, and the actual image/link/text under the pointer. Independent child controls retain their own target. The work covers title and episode cards, library and collections, downloads/local files/server sources, profiles and social content, readers, live channels, and page navigation without changing their card layouts or including ElegantFin work.

Why

• Keep Harbor's menu styling, translation and input conventions while centralizing measured placement, submenus, focus restoration and session-bound execution.
• Make Add idempotent and Move affect only the specified membership. Require acknowledged storage and validate collection publication/ownership rather than reporting memory-only success.
• Use exact download IDs and file paths, explicit episode scopes and fresh provider state. Report partial results and preserve records when a delete or persistence step fails.
• Add an image viewer with zoom/pan and real image save/copy operations. Public image links have separate eligibility checks; copying an image never means copying its URL.
• Preserve native editing behavior. A Windows WebView2 bridge covers transferable sandboxed Canvas image/link content without weakening sandbox isolation; unsupported frame content retains native tools.

Verification

The detailed coverage and limitations are in docs/context-actions-review.md. Tests use isolated storage, mocked account services and dedicated temporary files; no real account writes or user-file deletion were used for QA.

• Changed-file pnpm run check and TypeScript checks passed, with the recorded pre-existing gamepad lint warning.
• The full frontend suite ran 1,283 tests: 1,253 passed, the same nine failures recorded on the untouched base remain, and 21 were skipped. This is not an all-green claim.
• Windows cargo check passed with three existing dead-code warnings; four native policy tests passed.
• The isolated Windows native fixture passed eight probes, including pixel-exact clipboard round-trip, loopback image loading, editing-command filtering and sandboxed HTTP/blob context metadata/fallback.
• Full-application browser checks covered right-click/Shift+F10, image submenu and focus return, truthful image failure, additive membership, Move to an existing destination, persistence in a fresh tab, Arabic RTL placement, and dismissal without activating the sidebar underneath.
• Built the full isolated Windows application, separately from the fixture. Startup/shutdown smoke verification and the exact final artifact are recorded in the review document.

Final GitHub Code Quality run on c3fc27a0:

• Frontend formatting/lint and typecheck passed on Ubuntu. Its test result exactly matched Windows: 1,253 passed, nine baseline failures and 21 skipped.
• Linux cargo check and cargo test passed: 187 tests passed, zero failed, two ignored. This establishes native compilation/unit-test coverage; it does not replace a Linux desktop build/runtime trial.
• The overall workflow remains red solely because of the documented baseline frontend test failures.

Platform Impact

Windows native fixture and full-application startup were exercised. Native Save-dialog interaction, actual local playback/reveal, the full-app asynchronous frame bridge, real connected-provider writes and physical remote/gamepad checks remain manual acceptance items.

The Linux system build was attempted with the Linux target, but this Windows host lacks x86_64-unknown-linux-gnu; no Linux binary or runtime verification is claimed. macOS/mobile runtime checks are also outstanding. Native Canvas interception is intentionally Windows-specific; fallback behavior remains on other platforms.

Unsafe Simkl membership-only removal/unwatch operations remain blocked rather than deleting a whole title/history entry. Cross-family Move, universal cross-tab Back history and an invented Follow/Unfollow service are not included.

AniList/MyAnimeList progress informs the read state, but these context-menu writes do not synchronize progress back to those services. Connected services receive named unsupported outcomes instead of a silent success claim; individual-episode actions do not invent a sequential-progress update.

UI Changes

This is a draft for code review and isolated desktop trial. Before/after screenshots and a short interaction recording are still required before marking it ready. Existing screenshots containing user accounts were not uploaded.

Checklist

• This pull request is focused and contains no unrelated refactors.
• I ran vp check for the changed files.
• I ran the TypeScript check after TypeScript changes.
• I ran the relevant Cargo checks after Rust changes.
• I completed all affected-platform manual acceptance checks.
• I completed physical remote/gamepad and playback regression verification.
• I added or updated tests for behavior changes.
• No secrets, tokens, private URLs or personal account data are included in the submitted artifacts.