refactor(observability): re-home telemetry + monitoring onto aragora.observability (VAL-P4A-010/011)

[scarmani]

What

Re-home the telemetry and monitoring originals into aragora.observability, leaving deprecation-warning re-export shims at the old import paths. Part of the P4a layering foundation (milestone p4a-layering-foundation).

• aragora/telemetry/collector.py → moved to aragora/observability/telemetry_collector.py; old path is now a pure re-export shim.
• aragora/telemetry/research_events.py → moved to aragora/observability/research_events.py; old path is now a pure re-export shim.
• aragora/telemetry/__init__.py keeps its existing observability re-exports and now emits a DeprecationWarning.
• aragora/monitoring/simple_observer.py (SimpleObserver) → moved to aragora/observability/simple_observer.py; old path + package __init__ are two-sided shims emitting DeprecationWarning.

No caller migration: aragora.telemetry already had zero internal callers (floor stays 0), and the single aragora.monitoring consumer (aragora/server/handlers/admin/health/detailed.py) intentionally stays on the shim (ceiling stays at 1).

Behavior

All previously-working import paths keep working unchanged; the only new runtime behavior is a DeprecationWarning on import of the legacy modules. The moved originals are byte-identical to their previous content (the telemetry collector differs by exactly one internal import line repointed to the new research-events home).

Fulfills

• VAL-P4A-010: aragora/telemetry/* is now original-code-free (pure re-export shims), old paths import, aragora.telemetry emits a telemetry DeprecationWarning, internal caller floor stays 0.
• VAL-P4A-011: aragora/monitoring/* retired into observability with a two-sided shim, old path + new home import, aragora.monitoring emits a monitoring DeprecationWarning, caller ceiling stays at 1.

Validation (run in worktree with PYTHONPATH=<wt>)

• T3 (pure shim) + T5 (allowed-imports) PASS for every tracked aragora/telemetry/*.py and aragora/monitoring/*.py.
• T4 deprecation: aragora.telemetry (token telemetry), aragora.monitoring (token monitoring), plus the submodule shims, all PASS.
• Old paths import: from aragora.telemetry import get_logger; from aragora.telemetry.collector import TelemetryCollector, get_telemetry_collector; from aragora.telemetry.research_events import TelemetryEvent, TelemetryEventType → ok. from aragora.monitoring import SimpleObserver → ok.
• Caller floor (telemetry) = 0; caller ceiling (monitoring) = 1 (detailed.py).
• ruff check + ruff format --check: clean. Changed-file mypy: no errors in the 8 changed files. make test-smoke: pass. Targeted pytest tests/telemetry tests/monitoring: 160 passed.

Risks

Low. Behavior-neutral move + shims; the only consumer of the moved code remains functional via the shim. Generated files docs/METRICS.md and aragora/module_tiers.yaml are intentionally NOT regenerated here (both are path-frozen by open PRs #8460/#8461/#8382); the structural drift is deferred to the phase merge-train's single consolidated regen.

[github-actions]

Aragora Code Review

Advisory-only review. No issues found.

[scarmani]

Claude independent model review

Reviewer: claude (anthropic) — independent adversarial model review via the Aragora Claude reviewer, grounded on the exact PR head.
Head: 00c0fe7 (00c0fe7), committed 2026-06-29T04:41:08Z.
PR: #8690.
Model family: claude

Verdict: PASS

Verified the truncated shims against the pre-PR symbol sets, smoke-tested every import path, and checked for cycles, consumers, and filterwarnings=error. The moves are verbatim, both shims re-export the complete original public surface (research_events: 2 classes + 12 constructors; collector: TelemetryBackend/InMemoryBackend/TelemetryCollector/get_/set_telemetry_collector/record_event), class identity is preserved so cross-path isinstance still holds, no import cycle, and the one live consumer (server/handlers/admin/health/detailed.py) still resolves. No correctness or regression issues.

• [P3] aragora/monitoring/__init__.py:13-17 — the warnings.warn text says "import from aragora.observability instead," but SimpleObserver is not exposed at the package level (confirmed from aragora.observability import SimpleObserver raises ImportError); only aragora.observability.simple_observer works. Point the message at the submodule like the other three shims do, or add it to aragora/observability/__init__.
• [P3] aragora/server/handlers/admin/health/detailed.py:349 — the sole in-repo caller still imports via the deprecated aragora.monitoring.simple_observer path, so this PR ships a self-inflicted DeprecationWarning; cheap to repoint to aragora.observability.simple_observer now.

dogfood: yes