Section edit pens, cursor-driven piecewise scroll sync, URL-following editor.

Anchored h1/h2s carry data-line (markdown source line, top-level
headings only) and h2s get dimmed section pens that open the page
editor at that section. Editor scroll sync is now piecewise-linear
keyed on those anchors: the page follows the cursor (fractional,
wrap-aware, fixed window anchor; editor scroll no longer drives it),
the editor follows page scroll with a progress-based viewport anchor,
so document ends line up exactly in both directions. The editor always
follows the URL — fetch-navigation retargets it — with unsaved text
stashed per path for the session and restored on return. Banner pen
removed (the tab stays in the shell); top-right order is now
analytics, site settings, login/logout.

docs/design-principles.md

@@ -46,7 +46,7 @@ Pagerite is a single-user CMS/blog. This document records the initial high-level
 
 - Editing happens **in place**, in two modes opened by two pens:
   - **Page mode** — the 🖊️ next to a page's heading (including 404s, which is how new pages start) opens a CodeMirror Markdown editor docked to the left of the article: the panel is fixed to the viewport's left edge (its top tracks the banner's bottom until the banner scrolls away), the content shifts right and the sidebar hides while editing. Preview renders server-side per keystroke (no debouncing) and swaps the whole visible article content in one go (the edit pen and category cards survive the swap).
-  - **Site mode** — the 🖊️ on the banner opens a panel with the site **brand** (applied to the header live), a **theme** selector (swapping the theme stylesheet in place), **font** picks (heading/body/brand — stored as plain `:root` rows inside the custom CSS, referencing the base stylesheet's per-family font variables), a **site-wide custom CSS** field (injected into `<style id="pagerite-user">` in the live page head and swapped during fetch-navigation), the page's **banner design** selector (inherit / none / any design found on disk, inherited by children), the page's **banner HTML** field (supplementing the design, previewed into the real banner region, so you see exactly which banner you're editing) and the **structure tree**. Everything saves immediately as you edit — no save button, no edit mode.
+  - **Site mode** — the ⚙️ at the top right (after the 📊 analytics link, before login) opens a panel with the site **brand** (applied to the header live), a **theme** selector (swapping the theme stylesheet in place), **font** picks (heading/body/brand — stored as plain `:root` rows inside the custom CSS, referencing the base stylesheet's per-family font variables), a **site-wide custom CSS** field (injected into `<style id="pagerite-user">` in the live page head and swapped during fetch-navigation), the page's **banner design** selector (inherit / none / any design found on disk, inherited by children), the page's **banner HTML** field (supplementing the design, previewed into the real banner region, so you see exactly which banner you're editing) and the **structure tree**. Everything saves immediately as you edit — no save button, no edit mode.
 - Clicking a pen again closes the editor (without saving; a dirty preview reloads the page). The pens are `<button>`s wired up by `pagerite.js` — editing is an action, not a navigation. The editor's WebSocket **reconnects automatically** with local text and pending saves preserved. (All users are trusted authors for now; access control later with SSO.)
 - **CodeMirror 6** for Markdown editing (no WYSIWYG), title/published controls. Images can be pasted straight into the editor or chosen via a file input: they upload to the content store (`PUT /_api/files/...`) and insert `![alt](/_f/hash.ext)` at the cursor.
 - The **structure panel** (vue-draggable tree of the whole site, in site mode) covers page management: reorder any menu level, drag across sections, add, delete (two clicks: the button arms, then deletes — no dialogs). Every node is a real label — content-less category rows offer a ➕ to give them a landing page. Deleting a category removes only its landing page (the label and its subpages stay). Every non-empty list ends with a ➕ row that starts a new page as a local-only tree row at that level; the row can be dragged into place before its title and slug are filled in and is persisted only on commit. While dragging, these ➕ rows double as "end of this list" drop targets; dropping ON the lower part of a row makes the page that row's first child (even a leaf's, creating a sublist), while a row's exposed top edge inserts a sibling before it. A dragged row's indentation previews the target list's depth. Rows are always editable: titles save while typing, slug edits commit on blur/Enter since they rename the path (moving the whole subtree). The front page is the root row with an empty slug — renaming it away leaves no front page ("/" redirects to the first nav item), and giving another top-level row the empty slug makes it the front page.