Add Atlas Stream Processing commands

[nickpoindexter]

Summary

Adds first-class driver support for Atlas Stream Processing (ASP), implementing the ASP driver spec. Users currently have to drop down to
Manager::executeCommand against a workspace endpoint; this PR adds a dedicated client/handles/operations layer matching the patterns used by Client / Database / Collection.

What's new

Public API (src/)

• MongoDB\StreamProcessingClient — workspace-scoped client distinct from MongoDB\Client. Validates the workspace URI (atlas-stream-*.a.query.mongodb.net), enforces TLS, defaults authSource=admin, and rejects
  mongodb+srv://.
• MongoDB\StreamProcessors — create() / get() / getInfo() for managing processors in a workspace.
• MongoDB\StreamProcessor — start() / stop() / drop() / stats() / getStreamProcessorSamples() for a named processor.
• MongoDB\Model\StreamProcessorInfo — typed accessor over the getStreamProcessor response. Fields the spec marks Optional (e.g. id, pipelineVersion) return null when the server omits them.
• MongoDB\Model\StreamProcessorSamples — result of getStreamProcessorSamples(), exposes cursorId, documents, isExhausted().

Operation layer (src/Operation/StreamProcessing/)
One Operation class per wire command: createStreamProcessor, startStreamProcessor, stopStreamProcessor, dropStreamProcessor, getStreamProcessor, getStreamProcessorStats, startSampleStreamProcessor,
getMoreSampleStreamProcessor. Retryable reads (getStreamProcessor, getStreamProcessorStats) use executeReadCommand; everything else uses executeCommand per the spec's retryability matrix. All commands target the
admin database.

Notable spec / server alignment

• startAfter (in StartStreamProcessorOptions) is intentionally NOT serialized — the spec marks it RESERVED for future use and explicitly forbids drivers from sending it.
• Dev-server response shape deviations are accommodated, matching the workarounds in the Python POC:
  • GetStreamProcessor unwraps {ok: 1, result: {…}} when the server wraps the response.
  • GetMoreSampleStreamProcessor accepts both nextBatch (spec) and messages (current dev server).
  • StreamProcessorInfo::getId() / getPipelineVersion() return null when the server omits the field.
• getStreamProcessorSamples() is a single-command dispatch: absent/zero cursorId → startSampleStreamProcessor; non-zero cursorId → getMoreSampleStreamProcessor. Callers stop when the returned cursorId === 0.
• Internal-only fields like tenantID / projectId are not surfaced in the user-facing API.

Test plan

• composer check:cs — clean
• composer check:rector — clean (0 rule violations on new files)
• composer check:psalm — clean against updated baseline. The 11 new baseline entries are all MixedAssignment from reading untyped array $options / array $info, matching the pattern already established for every
  other Operation class.
• Unit tests under tests/StreamProcessing/ cover constructor-option type validation for every Operation, URI/TLS validation for the client, and model getters. Run with vendor/bin/phpunit --filter StreamProcessing.
• Functional smoke test StreamProcessingFunctionalTest exercises the full create → start → stats → sample → stop → drop lifecycle. Self-skips unless MONGODB_STREAM_PROCESSING_URI is set to a real workspace endpoint —
  needs an Evergreen variant or a workspace-aware tester to actually exercise.

Out of scope (per spec)

Deferred to a follow-up: modifyStreamProcessor, listStreamProcessors, listStreamConnections, processStreamProcessor, listWorkspaceDefaults. Users who need these today can still send them via Manager::executeCommand.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 53.87454% with 125 lines in your changes missing coverage. Please review.
✅ Project coverage is 86.37%. Comparing base (2628950) to head (ac657c9).
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
src/StreamProcessor.php	15.62%	27 Missing ⚠️
.../StreamProcessing/GetMoreSampleStreamProcessor.php	14.28%	18 Missing ⚠️
...peration/StreamProcessing/StartStreamProcessor.php	59.09%	18 Missing ⚠️
...eration/StreamProcessing/CreateStreamProcessor.php	39.13%	14 Missing ⚠️
...ation/StreamProcessing/GetStreamProcessorStats.php	20.00%	12 Missing ⚠️
...on/StreamProcessing/StartSampleStreamProcessor.php	20.00%	12 Missing ⚠️
.../Operation/StreamProcessing/GetStreamProcessor.php	0.00%	11 Missing ⚠️
src/StreamProcessors.php	60.00%	6 Missing ⚠️
...Operation/StreamProcessing/DropStreamProcessor.php	0.00%	3 Missing ⚠️
...Operation/StreamProcessing/StopStreamProcessor.php	0.00%	3 Missing ⚠️
... and 1 more

Additional details and impacted files

@@             Coverage Diff              @@
##               v2.x    #1898      +/-   ##
============================================
- Coverage     87.72%   86.37%   -1.36%     
- Complexity     3328     3472     +144     
============================================
  Files           454      467      +13     
  Lines          6656     6927     +271     
============================================
+ Hits           5839     5983     +144     
- Misses          817      944     +127     

Flag	Coverage Δ
6.0-replica_set	85.28% <53.87%> (-1.28%)	⬇️
6.0-server	81.49% <53.87%> (-1.13%)	⬇️
6.0-sharded_cluster	?
8.0-replica_set	86.27% <53.87%> (-1.32%)	⬇️
8.0-server	82.20% <53.87%> (-1.16%)	⬇️
8.0-sharded_cluster	?

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