various css fixes, fix new image loading bug when previewing, path docs

content/advanced/paths.md

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+---
+title: Paths in Quartz
+---
+
+Paths are pretty complex to reason about because, especially for a static site generator, they can come from so many places.
+
+The current browser URL? Technically a path. A full file path to a piece of content? Also a path. What about a slug for a piece of content? Yet another path.
+
+It would be silly to type these all as `string` and call it a day as it's pretty common to accidentally mistake one type of path for another. Unfortunately, TypeScript does not have [nominal types](https://en.wikipedia.org/wiki/Nominal_type_system) for type aliases meaning even if you made custom types of a server-side slug or a client-slug slug, you can still accidentally assign one to another and TypeScript wouldn't catch it.
+
+Luckily, we can mimic nominal typing using [brands](https://www.typescriptlang.org/play#example/nominal-typing).
+
+```typescript
+// instead of 
+type ClientSlug = string
+
+// we do
+type ClientSlug = string & { __brand: "client" }
+
+// that way, the following will fail typechecking
+const slug: ClientSlug = "some random slug"
+```
+
+While this prevents most typing mistakes *within* our nominal typing system (e.g. mistaking a server slug for a client slug), it doesn't prevent us from *accidentally* mistaking a string for a client slug when we forcibly cast it.
+
+Thus, we still need to be careful when casting from a string to one of these nominal types in the 'entrypoints', illustrated with hexagon shapes in the diagram below.
+
+The following diagram draws the relationships between all the path sources, nominal path types, and what functions in `quartz/path.ts` convert between them.
+
+```mermaid
+graph LR
+    Browser{{Browser}} --> Window{{Window}} & LinkElement{{Link Element}}
+    Window --"getCanonicalSlug()"--> Canonical[Canonical Slug]
+    Window --"getClientSlug()"--> Client[Client Slug]
+    LinkElement --".href"--> Relative[Relative URL]
+    Client --"canonicalizeClient()"--> Canonical
+    Canonical --"pathToRoot()"--> Relative
+    Canonical --"resolveRelative()" --> Relative
+    MD{{Markdown File}} --> FilePath{{File Path}} & Links[Markdown links]
+    Links --"transformLink()"--> Relative
+    FilePath --"slugifyFilePath()"--> Server[Server Slug]
+    Server --> HTML["HTML File"]
+    Server --"canonicalizeServer()"--> Canonical
+    style Canonical stroke-width:4px
+```