Feat: Serve bad.webp instead of an AI image when free.* finds nothing

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

README.md

@@ -44,7 +44,7 @@ https://direct-img.link/orange+cat?i=2
 - Leading zeros are ignored (`?i=02` = `?i=2`)
 - Only images that download count, so broken links and deleted photos are skipped and every `i` is a different image. `?i=2` is the 2nd working image
 - Higher `i` values take a little longer the first time, since the working images before it are downloaded to count them
-- If there aren't `i` working images, an [AI image](#ai-images) is served instead (except on [free.](#free-images) with a `src`, which serves `bad.webp`)
+- If there aren't `i` working images, an [AI image](#ai-images) is served instead (except on [free.](#free-images), which serves `bad.webp`)
 - Each `i` is cached separately. A search's results are kept for **1 hour**, so other `i` values of the same query within that hour don't search again and **don't count toward the limit**. One that was already counted downloads only its own image
 
 ## Query Normalization
@@ -85,7 +85,7 @@ Literal slashes (`/`) and dots (`.`) in the URL path are **rejected** to prevent
 - **Fragments (`#...`)** are never sent to the server by browsers
 - **Double-encoded values** are decoded once — `%2520` becomes `%20` (literal), not a space
 - Two queries that normalize to the same string share the same cached image
-- **Nothing found?** If a search finds no image (or fewer than `i` working ones), an [AI image](#ai-images) of the query is served instead of `bad.webp`, and cached like any other image. `bad.webp` is only served if the AI image fails too, or on [free.](#free-images) with a `src`
+- **Nothing found?** If a search finds no image (or fewer than `i` working ones), an [AI image](#ai-images) of the query is served instead of `bad.webp`, and cached like any other image. `bad.webp` is only served if the AI image fails too, or on [free.](#free-images)
 - **Out of searches?** If Brave refuses (e.g. its monthly spending limit is reached), Bing is searched instead. If Bing is blocking us too, `donate.webp` is served instead of an AI image, and nothing is cached, so the query works again once either is back
 
 ## Free Images
@@ -105,7 +105,7 @@ Need images you can publish? `free.direct-img.link` only serves images marked **
 
 - Both are optional and can be used alone or together, in any order (`?i=2&src=wikimedia` = `?src=wikimedia&i=2`)
 - `i` above `20` serves `max-i.webp`, which lists each site's range. Other invalid values serve `bad.webp`
-- With a `src`, only that source's images are served: if it has no image (or fewer than `i` working ones), `bad.webp` is served (remembered for 24h) instead of an AI image. Without one, an AI image is served like on the main site
+- Only free images are served: if there's no image (or fewer than `i` working ones), `bad.webp` is served (remembered for 24h) instead of an AI image. With a `src`, only that source's images are searched
 - Each `src` + `i` + query combination is cached separately. Like the main site, other `i` values within an hour of a search reuse its results and don't count as searches
 
 **Sources:**
@@ -154,7 +154,7 @@ Limits change over time, so they aren't listed here. **Check the Rate Limits sec
 - **Cache hits are unlimited** (within the burst limit)
 - Other `?i=` values of a query searched in the last hour reuse its results, so they don't count (except on `ai.`, where each `i` is a new image)
 - If Brave's spending limit is hit, searches use Bing; if Bing also blocks us, `donate.webp` is served (not cached)
-- Searches that find nothing count toward the limit. If the AI image served instead fails too (or there's none, on `free.` with a `src`), the failure is remembered for 24h (`bad.webp`)
+- Searches that find nothing count toward the limit. If the AI image served instead fails too (or there's none, on `free.`), the failure is remembered for 24h (`bad.webp`)
 - A Cloudflare WAF burst limit applies to all requests (HTTP 429). Its counters are approximate (not shared perfectly across Cloudflare servers), so bursts may slip slightly past it
 
 ## Caching
@@ -234,7 +234,7 @@ Create in your Cloudflare dashboard:
 | `NTFY_URL` | ntfy.sh topic URL for alerts | Optional |
 | `GOATCOUNTER_URL` | GoatCounter site URL for image hit analytics (e.g. `https://direct-img.goatcounter.com`) | Optional |
 | `GOATCOUNTER_TOKEN` | GoatCounter API token with "Record pageviews" permission | Optional |
-| `AURORA_API_KEY` | Key for the [AuroraIMG-6M API](https://github.com/direct-img/AuroraIMG-6M) (AI images and the nothing-found fallback). Without it, `ai.` serves `bad.webp` and searches that find nothing serve `bad.webp` | Optional |
+| `AURORA_API_KEY` | Key for the [AuroraIMG-6M API](https://github.com/direct-img/AuroraIMG-6M) (AI images and the nothing-found fallback). Without it, `ai.` serves `bad.webp` and searches that find nothing serve `bad.webp` (as they always do on `free.`) | Optional |
 
 ### 6. WAF Rules
 
@@ -267,7 +267,7 @@ Every request looks up its key here first, and a cached image is served from tha
 | `FREE:<src or auto>:<i>:<query>` (e.g. `FREE:wikimedia:2:orange cat`) | free images |
 | `AI:<src>:<i>:<query>` (e.g. `AI:auroraimg-6m:2:frog wizard`) | AI images |
 
-An AI image served because a search found nothing is stored under the search's own key, like any other image. A search where that also fails, or a `free.` search with a `src` (which gets no AI image), stores an empty object with `err` custom metadata instead, which serves `bad.webp` for 24h. After that the query is searched again.
+An AI image served because a search found nothing is stored under the search's own key, like any other image. A search where that also fails, or a `free.` search (which gets no AI image), stores an empty object with `err` custom metadata instead, which serves `bad.webp` for 24h. After that the query is searched again.
 
 Add an object lifecycle rule in **R2 → direct-img-store → Settings** that applies to all prefixes and deletes uploaded objects after **90 days**. It's required: nothing else expires cached images.