fix: fail loud on missing emoji dir, stem collisions, and corrupt images

refresh() previously treated a missing assets/emojis folder (wrong cwd,
missing WorkingDirectory=/WORKDIR) as an empty one, silently deleting
every application emoji on the app every restart with no signal and no
way back (recreated emojis get new IDs). _scan_folder now raises
DPYAppEmojisError naming the absent path instead; a present-but-empty
folder still mirrors as before.

Two files sharing a name stem across extensions (check.png + check.gif)
used to silently collapse to one synced emoji via last-write-wins,
breaking the documented delete+re-add replace workflow with no error.
_scan_folder now raises DPYAppEmojisError naming both colliding files.

A valid extension with unrecognized magic bytes (truncated download,
mismatched format) made discord.py raise an anonymous
ValueError('Unsupported image type given') from create_application_emoji,
which the lib's (Forbidden, HTTPException) catch didn't cover, leaving
no way to tell which file in a large folder was broken. _scan_folder now
pre-flights the same magic-byte check discord.py itself uses and raises
ValueError naming the offending file before any create is attempted.

Also collapses the redundant Forbidden member in the create/delete except
clauses (Forbidden already subclasses HTTPException); log-then-raise
behavior is unchanged.

Bump 0.1.0 -> 0.1.1.

Signed-off-by: disqualifier <dev@disqualifier.me>

README.md

@@ -34,6 +34,12 @@ appmojis.list()                                       # ["success_mark", ...]
 Call `refresh()` at startup, or from a command, to re-sync on demand — the lib adds no
 commands of its own.
 
+A **missing** `assets/emojis` folder is not the same as an **empty** one: if the folder
+doesn't exist (wrong cwd, missing `WorkingDirectory=`/`WORKDIR`), `refresh()` raises
+`DPYAppEmojisError` naming the path instead of mirroring an empty desired set — which would
+otherwise delete every application emoji on the next restart. An empty-but-present folder is
+still honored as "delete everything."
+
 ## Dot-access vs `emoji()`
 
 `self.get` is a namespace whose attribute lookup returns the emoji by name. It lives apart
@@ -60,11 +66,22 @@ targets **`discord.py>=2.5`**.
 ## Contract (fail-loud)
 
 The module docstring (`help(dpy_appemojis)` / IDE hover) is the source of truth. Nothing is
-swallowed: an invalid emoji name from a bad filename or an oversized file raises `ValueError`
-naming the file; exceeding the 2000 cap raises `DPYAppEmojisError` **before** any create; a
-discord API error (`Forbidden` / `HTTPException`) propagates **unwrapped** so a partial sync
-never hides behind a silent success. `emoji(name)` / `get.<name>` for a name that wasn't
-synced raise `KeyError` / `AttributeError` (call `refresh()` first).
+swallowed:
+
+- an invalid emoji name from a bad filename, an oversized file, or a file whose bytes aren't
+  a recognized PNG/JPEG/GIF/WEBP image (corrupt, truncated, or mismatched extension) raises
+  `ValueError` naming the file
+- two files sharing a name stem across extensions (e.g. `check.png` and `check.gif`) raise
+  `DPYAppEmojisError` naming **both** files, instead of silently syncing one and dropping the
+  other
+- a missing `assets/emojis` folder raises `DPYAppEmojisError` naming the path (see above)
+  rather than mirroring an empty set
+- exceeding the 2000 cap raises `DPYAppEmojisError` **before** any create
+- a discord API error (`HTTPException`, which covers `Forbidden`) propagates **unwrapped** so
+  a partial sync never hides behind a silent success
+
+`emoji(name)` / `get.<name>` for a name that wasn't synced raise `KeyError` / `AttributeError`
+(call `refresh()` first).
 
 ## Versioning