fix(pam): render the history scope filter as a chip rather than a button group

[maxkpower]

Design review 2026-09-04: this should be the chip filter menu, following the other PAM pages. Unset maps to the All scope. No copy changes.

[codecov]

Codecov Report

❌ Patch coverage is 57.14286% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 56.05%. Comparing base (e7321e3) to head (2e0ec33).
⚠️ Report is 288 commits behind head on pam/uat.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
...ense/bit-web/src/app/pam/testing/story-fixtures.ts	0.00%	2 Missing ⚠️
...c/app/pam/access-requests/history-tab.component.ts	80.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           pam/uat   #23002      +/-   ##
===========================================
+ Coverage    55.74%   56.05%   +0.30%     
===========================================
  Files         4438     4467      +29     
  Lines       141404   143053    +1649     
  Branches     22371    22596     +225     
===========================================
+ Hits         78824    80184    +1360     
- Misses       56914    57118     +204     
- Partials      5666     5751      +85     

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