feat: Implement TUI for identity

[nborges-aws]

Note: This PR is built upon and depends on #1856. Should not be merged until previous PR is, at which point diff will correctly render.

Description

Adds read-only TUI screens for inspecting Identity credential providers

• identity api-key-credential-provider — interactive menu, list picker, and get detail view
• identity oauth2-credential-provider— interactive menu, list picker, and get detail view
• Read operations feature interactive view in TUI
• Write operations (create/update/delete) are CLI only. TUI features CliOnlyScreen, which points user at the equivalent CLI command (e.g. This operation is available in the CLI: agentcore identity api-key-credential-provider create --help)
• Adds optional maxPageSize to the PaginatedTablePicker. Identity list API caps maxResults at 20, which caused issues when calling list/get from a tall terminal. The calculation was based on terminal height and could easily exceed 20, resulting in service exceptions. Optional cap allows identity to pass max value of 20, while other primitives are unchanged.
• ReadMe updates: adds Identity to the interactive-TUI notes, documents the read-only + CLI-only-mutations behavior, and backfills the OAuth2 credential provider command tree entries I missed in feat: add OAuth2 provider support to identity #1856

Related Issue

Closes #

Documentation PR

Type of Change

• Bug fix
• New feature
• Breaking change
• Documentation update
• Other (please describe):

Testing

Manually tested the TUI with bun run start and interacting with the TUI screen. Also ran the full suite against latest HEAD after rebasing the refactor branch:

• bun test src/ (590 pass, 0 fail)

• bun run typecheck clean

• bun run lint:check clean

• bun run format:check clean

• bun run build

• I ran npm run test:unit and npm run test:integ

• I ran npm run typecheck

• I ran npm run lint

• If I modified src/assets/, I ran npm run test:update-snapshots and committed the updated snapshots

Checklist

• I have read the CONTRIBUTING document
• I have added any necessary tests that prove my fix is effective or my feature works
• I have updated the documentation accordingly
• I have added an appropriate example to the documentation to outline the feature, or no new docs are needed
• My changes generate no new warnings
• Any dependent changes have been merged and published -- Depends on feat: add OAuth2 provider support to identity #1856 which should be merged first

---

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[codecov-commenter]

Codecov Report

❌ Patch coverage is 92.54079% with 64 lines in your changes missing coverage. Please review.
✅ Project coverage is 95.67%. Comparing base (a08c73f) to head (f7c2ab7).
⚠️ Report is 1 commits behind head on refactor.

Files with missing lines	Patch %	Lines
...entity/oauth2-credential-provider/update/index.tsx	75.52%	35 Missing ⚠️
...entity/oauth2-credential-provider/create/index.tsx	84.96%	20 Missing ⚠️
...dentity/api-key-credential-provider/get/screen.tsx	97.82%	2 Missing ⚠️
...rs/identity/api-key-credential-provider/screen.tsx	33.33%	2 Missing ⚠️
...identity/oauth2-credential-provider/get/screen.tsx	97.87%	2 Missing ⚠️
src/components/CliOnlyScreen.tsx	95.45%	1 Missing ⚠️
...ers/identity/oauth2-credential-provider/screen.tsx	50.00%	1 Missing ⚠️
src/handlers/identity/screen.tsx	50.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##           refactor    #1886      +/-   ##
============================================
- Coverage     95.98%   95.67%   -0.32%     
============================================
  Files           208      228      +20     
  Lines          9636    10448     +812     
============================================
+ Hits           9249     9996     +747     
- Misses          387      452      +65     

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