docs: apply Codex doc-review findings for v1.58.0.0

Cross-model doc review (Codex, read-only) checked the v1.58.0.0 docs
against the shipped code. Fixes:

- howto + make-pdf SKILL: diagram source is preserved base64 in a
  data-gstack-source attribute, not an HTML comment (-- in mermaid
  arrows would corrupt a comment); fences must start at column 0;
  fence options example gains page=portrait; --to html "zero network
  refs" qualified (--allow-network deliberately keeps remote tags).
- /diagram description, README + docs/skills.md rows: the hand-drawn
  aesthetic belongs to the .excalidraw artifact; rendered SVG/PNG use
  mermaid's clean neutral theme (lib/diagram-render entry.ts pins
  theme: "neutral").
- CHANGELOG v1.58.0.0 wording: --strict coverage lists all five fatal
  classes (missing/remote/out-of-tree/oversized/non-regular); fences
  are vector SVG in pdf+html, 300dpi PNG in docx; hand-drawn claim
  scoped to the .excalidraw file.
- lib/diagram-render/README: Page API table gains __downscaleRaster.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

docs/howto-diagrams-and-formats.md

@@ -24,7 +24,10 @@ make-pdf generate doc.md out.pdf
 
 The fence renders as a **vector** diagram (crisp at any zoom, selectable
 text), with the `title` as caption and accessibility label. The raw mermaid
-source is preserved in an HTML comment inside the document for debugging.
+source is preserved base64-encoded in a `data-gstack-source` attribute on the
+figure for debugging and round-trips (an HTML comment would corrupt mermaid's
+`-->` arrows). One catch: the fence must start at **column 0** — indented
+fences (inside lists, for example) stay plain code blocks by design.
 
 **Fence options** (space-separated in the info string):
 
@@ -83,8 +86,10 @@ make-pdf generate doc.md out.docx --to docx
 ```
 
 - **`--to html`** writes ONE self-contained file: diagrams as inline SVG,
-  images as data URIs, zero network references, plus a screen-reading layer
-  (centered measure, padding). Email it, attach it, open it anywhere.
+  images as data URIs, zero network references (under the default offline
+  posture — `--allow-network` deliberately keeps remote image tags live),
+  plus a screen-reading layer (centered measure, padding). Email it, attach
+  it, open it anywhere.
 - **`--to docx`** is a content-fidelity export: headings, tables, code
   blocks, lists, and diagrams (embedded as 300dpi PNGs with alt text) carry
   over. Page-perfect layout does not — that's Word's job once it's open.

docs/skills.md

@@ -56,7 +56,7 @@ Detailed guides for every gstack skill — philosophy, workflow, and examples.
 | [`/setup-deploy`](#setup-deploy) | **Deploy Configurator** | One-time setup for `/land-and-deploy`. Detects your platform, production URL, and deploy commands. |
 | [`/gstack-upgrade`](#gstack-upgrade) | **Self-Updater** | Upgrade gstack to the latest version. Detects global vs vendored install, syncs both, shows what changed. |
 | [`/make-pdf`](#make-pdf) | **PDF Generator** | Turn any markdown file into a publication-quality PDF. Proper margins, page numbers, cover pages, clickable TOC. Mermaid/excalidraw fences render as vector diagrams; `--to html\|docx` for other formats. |
-| [`/diagram`](#diagram) | **Diagram Maker** | English in, diagram out: mermaid source + editable `.excalidraw` (open it on excalidraw.com) + rendered SVG/PNG. Hand-drawn aesthetic, fully offline. |
+| [`/diagram`](#diagram) | **Diagram Maker** | English in, diagram out: mermaid source + editable `.excalidraw` (open it on excalidraw.com, hand-drawn style) + rendered SVG/PNG. Fully offline. |
 | [`/ios-qa`](#ios-qa) | **iOS QA Lead** | Live-device iOS QA via USB CoreDevice tunnel + embedded StateServer. Reads Swift source, codegens accessors, drives the real iPhone. Optionally exposes the device over Tailscale for remote agents. |
 | [`/ios-fix`](#ios-fix) | **iOS Autonomous Fixer** | Closes the find→fix→verify loop on a real iPhone. Captures a reproducing snapshot, fixes the source, rebuilds, redeploys, verifies. |
 | [`/ios-design-review`](#ios-design-review) | **iOS Designer's Eye** | 10-dimension Apple HIG audit on a real iPhone. Rates each screen, says what would make it a 10. |