GeezerVison

Reverts #465 (merged squash commit c67e177).

What this removes

• src/agentex/lib/core/tracing/obs_ids.py (get_obs_mode / obs_correlation / sync_ddtrace_to_lgtm)
• the obs_correlation() tagging added to src/agentex/lib/core/tracing/trace.py

Stack note
#465 is the foundation of the obs stack; the dependent PRs #466 (W3C FastACP ingress), #467 (Temporal interceptor) and #471 (ddtrace dual-sync) import obs_ids / sync_ddtrace_to_lgtm. They are not merged to next, so nothing merged breaks — but they are now orphaned against next and left open intentionally, to be reworked or closed separately.

Why
Backing out the business-span ↔ observability-trace correlation approach pending the tracing-library redesign.

🤖 Generated with Claude Code

Greptile Summary

This PR reverts the business-span ↔ observability-trace correlation added in #465, removing obs_ids.py and the obs_correlation() call sites in both Trace and AsyncTrace. The revert is clean: no remaining imports or references to the deleted module exist anywhere in the merged next branch.

• obs_ids.py deleted: removes get_obs_mode(), _lgtm_ids(), _ddtrace_ids(), and obs_correlation() entirely.
• trace.py cleaned up: the import of obs_correlation and its two call sites (in Trace.start_span and AsyncTrace.start_span) are removed symmetrically; span creation reverts to using serialized_data without observability tag injection.

sequenceDiagram
    participant Caller
    participant Trace/AsyncTrace
    participant obs_ids (removed)
    participant Span

    Note over Trace/AsyncTrace,obs_ids (removed): Before revert (PR #465)
    Caller->>Trace/AsyncTrace: start_span(name, input, data)
    Trace/AsyncTrace->>obs_ids (removed): obs_correlation()
    obs_ids (removed)-->>Trace/AsyncTrace: {"obs.trace_id": ..., "obs.span_id": ...}
    Trace/AsyncTrace->>Span: create with merged data + obs tags

    Note over Trace/AsyncTrace,obs_ids (removed): After revert (this PR)
    Caller->>Trace/AsyncTrace: start_span(name, input, data)
    Trace/AsyncTrace->>Span: create with serialized_data only

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