Fix keyboard shortcuts needing a second press after opening a log or profile

[camd]

Problem

Some job-view keyboard shortcuts intermittently have to be pressed twice to take effect.

Root cause

The job view wraps all shortcuts in a single <Hotkeys> from react-hot-keys (ui/job-view/KeyboardShortcuts.jsx). That library keeps an internal isKeyDown latch to suppress key-repeat:

• a keydown sets the latch true (and swallows any further keydown while it's set);
• the latch is only cleared by a keyup that bubbles to document.body.

Three shortcuts open a new browser tab/window, moving focus off the page so their keyup is delivered to the new tab and never reaches document.body:

Key	Action
l	logviewer (target="_blank" link)
shift+l	raw log (target="_blank" link)
g	gecko profile (window.open(url, '_blank'))

After one of these, the latch stays stuck true, so the next shortcut is silently swallowed and must be pressed a second time.

Fix

Clear the latch when the window loses focus by synthesizing a keyup on document.body, so the next shortcut fires on the first press. This is general — it also covers alt-tabbing away or any window.open while a key is held.

Testing

• Added tests/ui/job-view/KeyboardShortcuts_test.jsx, which reproduces the stuck-latch (second keydown with no intervening keyup is swallowed) and verifies recovery after a blur.
• Verified live in the browser against staging data: driving the real react-hot-keys instance, keydown Vagrant dev environment #1 fired, keydown treeherder RDBS schemas #2 (no keyup) was swallowed, and keydown Vagrant dev environment and a django webapp skeleton #3 after a window blur fired again. Normal press→release→press cycles continue to fire on the first press.
• PinBoard_test.jsx (also renders KeyboardShortcuts) still passes.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.66%. Comparing base (835e437) to head (8e5c646).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #9710   +/-   ##
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  Coverage   82.65%   82.66%           
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  Files         627      627           
  Lines       36784    36789    +5     
  Branches     3280     3282    +2     
=======================================
+ Hits        30405    30410    +5     
  Misses       6229     6229           
  Partials      150      150           

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