Handle Escape for active annotation tools

[KirtiRamchandani]

Problem

• The annotation toolbar can be enabled from the keyboard/mouse, but pressing Escape only unselects existing editors and does not turn off the active tool when no editor is selected.

Root cause

• The editor keyboard manager handles Escape for selected or active editors, but there was no Escape path for the active tool mode itself.

Solution

• When an annotation editor mode is active and there is no active editor, selection, or drawing session to handle, Escape switches the editor mode back to none.
• Added integration coverage for the FreeText toolbar state and viewer mode after Escape.

Tests run

• npx prettier --check src/display/editor/tools.js test/integration/freetext_editor_spec.mjs
• npx eslint src/display/editor/tools.js test/integration/freetext_editor_spec.mjs --report-unused-disable-directives
• git diff --check
• npx gulp generic
• Focused browser smoke test against the built generic viewer for Escape deselecting the active FreeText tool

Fixes #20199

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.45%. Comparing base (5fbab91) to head (267313f).
⚠️ Report is 12 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #21375      +/-   ##
==========================================
- Coverage   81.45%   81.45%   -0.01%     
==========================================
  Files         260      260              
  Lines       65805    65809       +4     
==========================================
+ Hits        53600    53602       +2     
- Misses      12205    12207       +2     

Flag	Coverage Δ
fonttest	9.06% <ø> (ø)
integrationtest	66.73% <100.00%> (-0.02%)	⬇️
unittest	57.04% <0.00%> (+<0.01%)	⬆️
unittestcli	55.99% <0.00%> (-0.01%)	⬇️

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