Overhaul dandi-cli testing matrix with explicit schema_install dimension

[yarikoptic-gitmate]

Summary

• Introduces a schema_install matrix dimension (client / server / both) to explicitly control where dandischema is installed during dandi-cli integration tests
• Removes the useless dandi-devel mode (DANDI_DEVEL=1 does not affect dandi-cli tests) along with associated Python 3.10 entries and hdf5 installation steps
• Keeps vendorized (ember-dandi) testing, paired with schema_install: both

New matrix (9 jobs)

Scenario	OSes	dandi-cli version	Jobs
schema_install: client	windows, ubuntu, macos	master + release	6
schema_install: server	ubuntu	master	1
schema_install: both	ubuntu	master	1
schema_install: both + ember-dandi	ubuntu	master	1

This matches the desired testing matrix from the issue:

1. dandischema installed only into client (released and master)
2. dandischema installed only into server (master only)
3. dandischema installed into both (both masters)
4. vendorization setup with "both"

Coverage impact

None — only test-dandi-cli.yml is modified, and it does not report code coverage. The coverage-reporting workflows (test.yml, test-nonetwork.yml) are untouched.

Test plan

• Verify the workflow YAML parses correctly (validated locally with yaml.safe_load)
• Confirm schema_install: client jobs skip the Docker build step
• Confirm schema_install: server jobs skip the dandischema pip install step
• Confirm schema_install: both jobs run both dandischema install and Docker build
• Confirm vendorized (ember-dandi) job sets the correct env vars

Closes #351

https://claude.ai/code/session_01RgrGZVVM44FN7LnGhexiB9

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.92%. Comparing base (bf5c98e) to head (f80e8f8).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #396   +/-   ##
=======================================
  Coverage   97.92%   97.92%           
=======================================
  Files          18       18           
  Lines        2405     2405           
=======================================
  Hits         2355     2355           
  Misses         50       50           

Flag	Coverage Δ
unittests	97.92% <ø> (ø)

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[yarikoptic]

claude:

● Now verified from actual job logs. Here's the full checklist verification:                                                                                                                                                      
                                                                                   
  1. "Verify the workflow YAML parses correctly" -- Confirmed: yaml.safe_load parses without error.                                                                                                                               
                                                                                                                                                                                                                                  
  2. "Confirm schema_install: client jobs skip the Docker build step" -- Confirmed from job logs. Example: job 70937399933 (ubuntu, master, client) shows "Install dandischema into client" = success, "Build dandi-api image" =  
  skipped. Same pattern across all 6 client jobs.                                                                                                                                                                                 
                                                                                                                                                                                                                                  
  3. "Confirm schema_install: server jobs skip the dandischema pip install step" -- Confirmed from job 70937399934 (ubuntu, master, server): "Install dandischema into client" = skipped, "Build dandi-api image" = success.      
  
  4. "Confirm schema_install: both jobs run both dandischema install and Docker build" -- Confirmed from job 70937399935 (ubuntu, master, both): "Install dandischema into client" = success, "Build dandi-api image" = success.  
  Env var steps correctly skipped (non-ember).                    
                                                                                                                                                                                                                                  
  5. "Confirm vendorized (ember-dandi) job sets the correct env vars" -- Confirmed from job 70937399930 (ubuntu, master, both, ember-dandi): "Set DANDI_TESTS_INSTANCE_NAME" = success, "Set DANDI_TESTS_INSTANCE_IDENTIFIER" =   
  success, "Set DANDI_TESTS_DOI_PREFIX" = success. Both install and Docker build also ran.
                                                                                                                                                                                                                                  
  All 5 test plan items verified from actual CI job logs. The PR is green and ready to merge.    

coverage remained the same, CI is green , changes making sense overall, let's proceed