Fix: markdown-previewer - dark mode toggle not working

[dev-Aarish]

What does this PR do?

Fixes the dark mode toggle in the Markdown Previewer tool. The moon/sun button did nothing because a ReferenceError at script load (the view-restore block called setView() before let currentView was declared, i.e. a temporal-dead-zone violation) aborted the rest of the inline script — so toggleTheme() was never set up. Moved the state declarations (dark, currentView) above their restore blocks and fixed the view-persistence save to use the correct variable.

Closes #833

Type of Change

• New tool
• Enhancement to existing tool
• Bug fix
• Documentation update
• Build system / infrastructure

Screenshot

Checklist

• I have read the Contributing Guide
• My branch follows the naming convention (add/tool-name, feat/description, or fix/description)
• I have tested my changes locally in at least one modern browser

For new tools:

• The tool is a single self-contained .html file in the tools/ folder
• The filename is kebab-case (e.g. json-formatter.html)
• I added an entry to data/tools.json with all required fields
• I added a screenshot as tools/<tool-name>.png next to the HTML file
• No JS frameworks (React, Vue, Angular, etc.) or heavy UI libraries (Bootstrap JS, jQuery, etc.)
• CDN links for lightweight libraries and fonts are fine — no copy-pasting library source code inline
• I ran node scripts/sort-norm.js data/tools.json to sort and normalize the tools registry
• I ran node scripts/build.js and verified the landing page renders correctly

For enhancements / bug fixes:

• I have not introduced any external dependencies
• The tool still works as a standalone single HTML file

[praveenscience]

The three fixes are correct:

1. let dark = false moved above toggleTheme() call — fixes temporal dead zone issue
2. let currentView = "both" moved above setView() call — same fix
3. mode → currentView in localStorage.setItem — mode was out of scope (it is a parameter of setView(), not available at line 577)

Note: There is a remaining bug at lines 575–578 — setView("both") always overwrites the restored view from localStorage, and then saves "both" back, wiping the user preference. Will create a follow-up issue for this.