Fix mermaid click + zone-map TP links under the /wiki deploy subpath

[clouths]

Two classes of links 404'd on the live GitHub Pages project site (served under /wiki/) while working locally at the root:

1. Mermaid diagram click targets (item pages). The generators write them site-absolute (click b "/content/items/...") and they live in code-fence text, not href/src attributes — so both Zola and the CI rewrite pass skip them. The page script now prefixes them with the base path part (read from body[data-root], "" locally / /wiki deployed) at the single pre→div conversion point, so both data-src and textContent carry the fixed source and refreshMermaid re-renders stay correct. No-op at the root.

2. Zone-map teleport links. The multi-destination selector links (map.js) and inlined-map single-destination links (zone-map.js) both read body[data-root] at parse time, but they load in <head> before <body> exists — so ROOT_PATH was "" forever and withRoot() a no-op. Made the read lazy (rootPath()) so the base path is picked up once the body is present.

Files

file	change
templates/base.html	fixMermaidClicks() prefixes site-absolute click URLs with the base path at the pre→div conversion (data-root pattern)
static/map.js	lazy rootPath() — body read at parse time was always null in <head>
static/zone-map.js	same lazy rootPath() fix
tests/subpath.spec.js	new — 5 tests (3 mermaid click + 2 zone-map TP), subpath project only
tests/mermaid.spec.js	root regression: click targets stay site-absolute + navigate at root
playwright.config.js	subpath testMatch/testIgnore now include subpath.spec.js

Tests

• New tests/subpath.spec.js (5 tests) runs in the subpath Playwright project, which mirrors the deploy (same build served under /wiki/ with the CI link rewrites + data-root).
• Root regression added to mermaid.spec.js proving click targets stay site-absolute and still navigate at the root.
• Full suite green locally: 186 passed, 77 skipped, 0 failed.

Follows the i18n subpath fix (#8); this branch is a single clean commit on main.