fix(instrumentation-py): repair Together, Vertex AI, and Watson Orchestrate ADK OTel 2.x spans

[Nightingalelyy]

Summary

• Repair the Python Together, Vertex AI, and Watson Orchestrate ADK instrumentation packages for the OpenTelemetry 2.x span contract.
• Add cooperative lifecycle ownership, exact-once stream handling, call-time parenting, canonical tools and usage, precise provider errors, and bounded privacy-safe serialization.
• Add real current-SDK exported-span regressions and a patch release intent for all three packages.

Validation

• Focused package tests: Together 11/11, Vertex AI 15/15, Watson Orchestrate ADK 11/11 (37/37).
• Root-config Ruff check and format check pass for all changed package source and tests.
• Release inventory and release-intent validation pass.
• All three package wheels build and import successfully; SHA-256: Together 1eb15d18..., Vertex AI d28ce0db..., Watson Orchestrate ADK 14a803f8....
• Exact editable direct_url.json entries point to the three local Group 27 package directories.
• All 22 companion example processes completed under otel2-fix-py-group-27-20260818T102109Z; 19 deterministic traces exported and three credential-gated live scripts skipped explicitly.
• Respan MCP audit opened all 19 trace trees and all 43 full details: 43 unique log IDs, 43 unique span IDs, one root per trace, exact counts, no orphans/duplicates, exact marker on every record, bounded payloads, correct streams/tools/usage/errors, and no forbidden aliases.

External follow-ups

• Current ingestion leaves convenience tools/tool_calls arrays empty despite canonical definitions/calls, derives some provider IDs from model namespaces, and projects native OTel 429/503/500 errors as success/200 with estimated tokens.
• Direct Together, authenticated Vertex AI, and live Watson service runs remain credential-gated.
• Release publication must synchronize the package manifests with the aggregate >=0.1.1 floors.

Companion examples

• fix(examples-py): validate Together, Vertex AI, and Watson Orchestrate ADK OTel 2.x spans respan-example-projects#75

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