Add conflict policy options: Skip / Auto-number / Override

New ConflictPolicy enum in rename/ (Skip = original/default behavior,
AutoNumber = save as "Name (1).ext" counting up to the first free slot,
Override = replace the conflicting file outright), threaded through
execute_renames/rename_one alongside RenameAction. Override never deletes
a conflicting directory (falls back to Skip for that case); AutoNumber
sidesteps directories the same way by just trying the next number.
execute_rename now takes a conflict argument; undo/history are
deliberately NOT conflict-aware and always use their own fixed
skip-on-conflict policy regardless of what the original rename used.

Frontend: a second segmented selector in the rename confirmation modal
("On conflict: Skip / Auto-number / Override"), with Override styled in
red and its warning copy calling out that it can't be undone.

README.md

@@ -9,14 +9,19 @@ native file/folder loading and drag-and-drop, local filename-based season/episod
 movie title/year* detection ("Match") is working, real online metadata lookups against
 TMDB ("Fetch Data") are working for both TV episodes and movies — including fuzzy
 title disambiguation, so a search that returns several similarly-named results doesn't
-just take TMDB's top-ranked hit — and the actual on-disk operation is wired up
-(skip-on-conflict, with a confirmation step showing the full old-path/new-path plan
-before anything touches disk, a per-row ✕ to drop an individual file from that plan at
-the last step, and a Move/Copy/Symlink selector for what to actually do at each
-target). It can also organize files into subfolders — including ones that don't exist
-yet — when the naming scheme includes a `/`. Every completed batch is logged to a
-history panel that can undo it (moving files back for Move, or just removing what was
-created for Copy/Symlink). A single loaded batch can freely mix TV episodes and movies
+just take TMDB's top-ranked hit — and the actual on-disk operation is wired up (with a
+confirmation step showing the full old-path/new-path plan before anything touches disk,
+a per-row ✕ to drop an individual file from that plan at the last step, a Move/Copy/
+Symlink selector for what to actually do at each target, and — independently — a Skip/
+Auto-number/Override selector for what happens when the computed name already exists:
+leave it alone (the original, and still default, behavior), save alongside it as
+"Name (1).ext", or replace it outright). It can also organize files into subfolders —
+including ones that don't exist yet — when the naming scheme includes a `/`. Every
+completed batch is logged to a history panel that can undo it (moving files back for
+Move, or just removing what was created for Copy/Symlink — undoing always uses its own
+skip-on-conflict policy regardless of what the original rename used, so an undo can
+never overwrite something else as a side effect). A single loaded batch can freely mix
+TV episodes and movies
 — each file only fills in the fields that apply to it. "Match" also parses release-tag
 text straight out of the filename — resolution, source (BluRay/HDTV/WEB-DL/…),
 video/audio codec, release group — so naming schemes can reference
@@ -110,9 +115,10 @@ to the source file's parent directory, never as an absolute path, and every path
 component is validated (`validate_relative_target`) to reject empty segments (a
 leading, trailing, or doubled `/` — which also catches an absolute-looking
 `/etc/passwd`-style path), `.`/`..` segments, and backslashes (Renamr always uses `/`
-for the naming scheme's folder separator regardless of OS). Conflict policy is
-unchanged: if the resolved target already exists and isn't the same underlying file,
-that item is skipped rather than overwritten.
+for the naming scheme's folder separator regardless of OS). If the resolved target
+already exists and isn't the same underlying file, what happens next is up to the
+chosen conflict policy — Skip (default), Auto-number, or Override; see item 6 of the
+porting roadmap below for the full behavior of each.
 
 ## Project layout
 
@@ -127,8 +133,9 @@ crates/renamr-core/   Pure Rust core: naming-expression engine (ported), local
                        search + episode lookup
                        and movie search + lookup, both disambiguated via `similarity/`,
                        tested against a mocked HTTP server via `mockito`), the on-disk
-                       rename engine (`rename/` — skip-on-conflict, Move/Copy/Symlink
-                       actions, can also organize into (auto-created) subfolders when
+                       rename engine (`rename/` — Move/Copy/Symlink actions,
+                       Skip/Auto-number/Override conflict policies, can also organize
+                       into (auto-created) subfolders when
                        the naming scheme includes `/`) — and a rename history/undo log
                        (`history/`, a partial `HistoryDialog` port, undo-aware of which
                        action produced each batch). Not yet ported: full media metadata
@@ -244,17 +251,22 @@ ported from, for anyone picking this up:
 6. **Rename engine + CLI** — `net.filebot.cli.CmdlineOperations` (1235 lines) and
    `ArgumentBean` (415 lines, the full flag surface: `-rename`, `--db`, `--format`,
    `--action`, `--conflict`, `-get-subtitles`, `-script`, etc.). The rename operation is
-   done (`crates/renamr-core/src/rename`, fixed skip-on-conflict policy, wired to the
-   UI's Rename button behind a confirmation step) including the `move`-into-subfolder
-   `--action` variant — a naming scheme like `{n}/{s00e00}` organizes files into
-   subfolders, creating any missing folders automatically, always scoped to the file's
-   own directory tree. The `copy`/`symlink` `--action` variants are done too — an action
-   selector in the confirmation modal picks Move/Copy/Symlink for the whole batch; Copy
-   and Symlink both leave the source file untouched and produce a new file/link at the
-   computed target, and both are undoable from the History panel the same as Move (undo
-   for Copy/Symlink just removes what was created, since there's nothing to move back).
-   Not yet done: the `--conflict` variants beyond skip (auto-number, override), and the
-   CLI flag surface itself.
+   done (`crates/renamr-core/src/rename`, wired to the UI's Rename button behind a
+   confirmation step) including the `move`-into-subfolder `--action` variant — a naming
+   scheme like `{n}/{s00e00}` organizes files into subfolders, creating any missing
+   folders automatically, always scoped to the file's own directory tree. The
+   `copy`/`symlink` `--action` variants are done too — an action selector in the
+   confirmation modal picks Move/Copy/Symlink for the whole batch; Copy and Symlink both
+   leave the source file untouched and produce a new file/link at the computed target,
+   and both are undoable from the History panel the same as Move (undo for Copy/Symlink
+   just removes what was created, since there's nothing to move back). The `--conflict`
+   variants are done too — a second selector in the same modal picks Skip (default,
+   leaves the conflicting file alone), Auto-number (`"Name (1).ext"`, counting up to the
+   first free slot), or Override (replaces the conflicting file outright — the one
+   irreversible option, called out with red styling in the UI; undoing that batch later
+   restores the *source*, never what got overwritten, since undo always uses its own
+   fixed skip-on-conflict policy no matter which policy the original rename used). Not
+   yet done: the CLI flag surface itself.
 7. **The rest of the UI** — the Rename panel (file loading, drag-drop, live preview,
    local TV/movie matching, confirmed rename with per-item exclude, rename history/undo,
    Align Up/Down reordering, naming-scheme Presets with `1`-`9` hotkeys) is built; the