Add "View patterns" context menu to log explorer

[tonyalaribe]

Summary

• Adds a "View patterns" option to field context menus in the log detail JSON tree and facets sidebar
• Navigates to the patterns visualization (viz_type=patterns) for the selected field
• Adds viewFieldPatterns JS helper function

Extracted from #300 to reduce PR size.

Test plan

• Open log explorer, expand a log entry, right-click a field → "View patterns" should navigate to patterns view for that field
• In facets sidebar, click field dropdown → "View patterns" should work similarly

[claude]

Code Review

Small, focused PR — easy to follow. A few observations:

1. Inconsistency in Log.hs: inline JS string vs. data-attribute pattern

The new facets dropdown item (line 434) passes the field path as an inline JS string literal:

onclick_ $ "viewFieldPatterns('" <> T.replace "___" "." key <> "')"

The sibling items (lines 393–426) already store the field via term "data-field" and access it via @data-field in Hyperscript. This item should follow the same convention, e.g.:

li_ $ a_ [class_ "flex gap-2 items-center", term "data-field" (T.replace "___" "." key),
           [__|on click call viewFieldPatterns(@data-field) end|]] do

Embedding a field name directly into a JS string literal (via Haskell string concatenation) is also a latent XSS vector — if a field name ever contains a single-quote, it would break out of the string. The data-attribute pattern avoids this entirely and is the established idiom in this file.

2. Utils.hs: onpointerdown_ vs Hyperscript on click

The new entry (Utils.hs:379) uses onpointerdown_ with a raw JS call. The non-filter context-menu actions ("Add as table column", "Group by") use Hyperscript on click. The filter items use onpointerdown_, so this pattern is not unique, but navigation triggered on pointerdown (before click fires) is an unusual UX choice worth confirming intentionally.

3. Minor: implicit pattern_skip deletion

url.searchParams.delete('pattern_skip');

A brief comment explaining why this param is reset on navigation would help future readers.

No structural issues

HTML structure, faSprite_ usage, and class lists are consistent with surrounding code.