👌 Sync tabs via change events, open on URL hash, persist choice

[chrisjsewell]

Three tabs-JS improvements, plus a new declarative config option.

Changes

• Click+drag on tab causes synced tabs to go out of sync #46 — sync via change events: synchronised-tab updates now hang off the radio input's change event instead of label.onclick, so click-drag releases and keyboard arrow selection sync correctly. Programmatic sync sets input.checked directly (never .click()), so no event cascades.
• Open tab when its :name: is used in URL #239 — URL fragments open tabs: a hash targeting a tab label (:name:) or any element inside a tab panel selects that tab — including walking up nested tab-sets so every enclosing panel opens and the target is actually visible — then scrolls it into view. Also handles hashchange without a reload. Deliberate decisions: hash selection does not propagate to synced siblings and is not persisted (a fragment names one specific tab).
• Support sticky tab selection #103 — persistent, configurable storage: selection storage moves from sessionStorage to localStorage (behaviour change: tab choice now survives new browsing sessions), with a new TOML-representable option sd_tabs_storage_prefix (default unchanged key prefix; empty string disables persistence — useful for shared origins like RTD subprojects). The value reaches the JS declaratively as a data- attribute on the script tag. Storage access is fully guarded: browsers that throw on localStorage (blocked site data, disabled storage) keep all tab functionality except persistence.
• Removed the stray console.log in the query-param path; fixed the header comment that wrongly claimed localStorage previously.

Verification

• Playwright runtime suite, 16/16 on the built docs: change-event sync both directions, hash opening (label, in-panel target, nested panels with visibility asserted, hashchange), localStorage persistence across a real reload, empty-prefix disable, storage-throwing browser still fully functional, and attribute HTML-escaping (a hostile prefix cannot break out of the tag).
• Independent review verified the config's rebuild="env" category empirically: changing the prefix and rebuilding incrementally updates the script tag on unrebuilt pages — no staleness. Hash precedence, same-group multi-set, unsynced named tabs, and non-tab hashes all probed clean.
• Full suite on pinned Sphinx 7.2.6 / 7.4.7 / 8.2.3 (175 passed each); add_js_file(**attrs) attribute forwarding verified on the 7.2.6 floor; tsc strict JSDoc green; new tests/test_tabs_js.py covers the script-tag attribute for default/custom/empty config plus DOM-order pinning.

Closes #46
Closes #239
Closes #103

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.74%. Comparing base (abbf459) to head (7625cc5).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #284      +/-   ##
==========================================
+ Coverage   90.72%   90.74%   +0.02%     
==========================================
  Files          13       13              
  Lines        1207     1210       +3     
==========================================
+ Hits         1095     1098       +3     
  Misses        112      112              

Flag	Coverage Δ
pytests	90.74% <100.00%> (+0.02%)	⬆️

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