Add Filter panel: narrow a loaded batch by extension, kind, filename, and season

Fully local, and adds no new Rust/Tauri commands at all - reuses pick_files plus the
same guess_episode/guess_movie/guess_release_info local matchers "Match" already calls
in the Rename panel, just applied to a second, independently-loaded file list and
rendered as toggleable filter criteria instead of a rename preview.

New src/components/FilterPanel.tsx/.css: Load Files scans the batch immediately,
toggleable chips appear for every extension and media kind actually present, a
filename-contains text field and a season number field (TV only) narrow further, and
Copy File Paths exports whatever currently matches to the clipboard.

Verified with a 21-check Playwright script against npm run dev (chip toggling, the
filename/season filters, the no-match empty state, and the clipboard export).

README.md

@@ -48,7 +48,10 @@ whichever TV source (TMDB/TVmaze/OMDb) is already configured in Fetch Data Setti
 separate credentials needed; see "Episodes" below. A new SFV panel computes and verifies
 CRC32/MD5/SHA1 checksums for a loaded set of files, and reads and writes the classic
 `.sfv`/`.md5`/`.sha1` sidecar-file formats — entirely local, no network access or
-credentials of any kind; see "SFV" below. See "Porting roadmap" below.
+credentials of any kind; see "SFV" below. A new Filter panel loads a batch of files and
+narrows it down by extension, TV/Movie/Unmatched kind, filename text, and (for TV) season
+— all computed from the same local, filename-only matching "Match" uses, with a Copy File
+Paths export for whatever's left; see "Filter" below. See "Porting roadmap" below.
 
 The naming scheme is fully user-editable from the app (the "Naming Scheme" button next
 to the New Names list) — the default is `{show name} - {season number}x{episode
@@ -244,7 +247,14 @@ src/                   React + TypeScript UI (Vite). Faithful recreation of the
                        checksum file and verify the files it lists against what's
                        actually on disk (OK/mismatch/missing per entry) — no settings
                        modal at all, since the feature needs no credentials or network
-                       access.
+                       access. `FilterPanel.tsx` is the fourth: load a set of files and
+                       narrow them down with toggleable extension/kind chips, a
+                       filename-contains text field, and a season number field (TV
+                       only) — adds no new Rust/Tauri commands at all, reusing
+                       `pick_files`/`guess_episode`/`guess_movie`/`guess_release_info`
+                       exactly as the Rename panel's own "Match" does, just applied to
+                       a second, independently-loaded file list and rendered as
+                       criteria instead of a rename preview.
 scripts/gen_icons.py   Regenerates src-tauri/icons/ from the real logo mark
                        (`scripts/logo/icon-source.png`, cropped from the supplied
                        lockup) — replace that source image to change the look.
@@ -441,6 +451,26 @@ resolved against the real files sitting next to it on disk and reported as **OK*
 referenced file isn't there). Checksum comparison is case-insensitive, since some tools
 write hex digests in uppercase and others in lowercase.
 
+## Filter
+
+The Filter sidebar panel loads a batch of files (independent of whatever's loaded in the
+Rename panel) and narrows it down before you decide what to do with it elsewhere — copy
+the matching paths out, or just get a sense of what's actually in a folder. Unlike SFV,
+it adds no new Rust/Tauri code at all: it scans every loaded file with the exact same
+local, filename-only matchers "Match" uses (`guess_episode`/`guess_movie`/
+`guess_release_info`) and turns the results into filter criteria instead of a rename
+preview — no network calls, so scanning even a large batch is effectively instant.
+
+**Load Files…** loads and scans a batch in one step. Toggleable chips then appear for
+every **extension** actually present (e.g. MKV/MP4/TXT) and every **kind** Aurora Curator
+locally recognized (TV/Movies/Unmatched) — click a chip to exclude that group, click it
+again to bring it back. A **filename contains** field does a live, case-insensitive
+substring search, and a **season** field (shown only while the TV chip is enabled) narrows
+to a single season number, automatically excluding anything that isn't a TV episode in
+that season. The results list updates live with an "N of M files match" count, and
+**Copy File Paths** writes every currently-matching file's full path, one per line, to the
+clipboard.
+
 ## Porting roadmap (not yet done)
 
 Roughly in priority order — each references the original FileBot source file it's
@@ -542,11 +572,13 @@ ported from, for anyone picking this up:
    Align Up/Down reordering, naming-scheme Presets with `1`-`9` hotkeys) is built, and so
    are the Subtitles panel (search + download via OpenSubtitles, see "Subtitles" above),
    the Episodes panel (series search + season browse with a Copy list export, no
-   credentials of its own, see "Episodes" above), and the SFV panel (compute/verify
+   credentials of its own, see "Episodes" above), the SFV panel (compute/verify
    CRC32/MD5/SHA1 checksums, read/write `.sfv`/`.md5`/`.sha1` sidecar files, entirely
-   local with no credentials at all, see "SFV" above) — the first three of the other
-   five sidebar panels to become real screens. The remaining two (Filter/List) are
-   still stub screens. Align Up/Down is button-based
+   local with no credentials at all, see "SFV" above), and the Filter panel (extension/
+   kind/filename/season narrowing over a locally-scanned batch, no new Rust/Tauri
+   surface at all, see "Filter" above) — the first four of the other five sidebar
+   panels to become real screens. The remaining one (List) is still a stub screen.
+   Align Up/Down is button-based
    (swaps the selected file with its neighbor), not the original's
    drag-and-drop-within-a-list interaction.
 8. **Undo/history for renames** — done, as a flat JSON-backed undo stack rather than a