fix(debugging): support probes on declarations

[tylfin]

Description

Allow Dynamic Instrumentation line probes placed on function or method declarations to install successfully. Function discovery records code-object header ranges and redirects these probes to the first executable line without parsing application source. The configured source line remains unchanged in emitted probe metadata and the effective line is retained for probe removal.

Testing

• Dynamic Instrumentation debugging suite on Python 3.12: 528 passed, 4 skipped
• scripts/lint checks
• Targeted formatting and type checks
• Reno lint and release-note spelling checks

Risks

Code-object line metadata can differ between Python versions. The fallback is limited to locations that resolve to exactly one function header, while ordinary executable-line probes retain their existing behavior.

[cit-pr-commenter-54b7da]

Circular import analysis

⚠️ Existing circular imports

There are 3 circular imports that already exist on the base branch and have not been changed by this PR.

ddtrace.llmobs -> ddtrace.llmobs._evaluators -> ddtrace.llmobs._evaluators.format -> ddtrace.llmobs._experiment -> ddtrace.llmobs
ddtrace.errortracking._handled_exceptions.bytecode_injector -> ddtrace.errortracking._handled_exceptions.callbacks -> ddtrace.errortracking._handled_exceptions.collector -> ddtrace.errortracking._handled_exceptions.bytecode_reporting -> ddtrace.errortracking._handled_exceptions.bytecode_injector
ddtrace.appsec._asm_request_context -> ddtrace.appsec._iast._iast_request_context_base -> ddtrace.appsec._iast._iast_env -> ddtrace.appsec._iast.reporter -> ddtrace.appsec._exploit_prevention.stack_traces -> ddtrace.appsec._asm_request_context

[cit-pr-commenter-54b7da]

Dependency direction analysis

⚠️ Existing dependency direction violations

There are 249 dependency direction violations that already exist on the base branch and have not been changed by this PR.

Show existing violations (showing 5 of 249 highest severity)

ddtrace.internal.tracemethods -×-> ddtrace.trace  (internal-core -> product:tracing, score=135)
ddtrace.llmobs._integrations.anthropic -×-> ddtrace.trace  (product:llmobs -> product:tracing, score=133)
ddtrace.appsec._listeners -×-> ddtrace.trace  (product:appsec -> product:tracing, score=133)
ddtrace.llmobs._integrations.openai -×-> ddtrace.trace  (product:llmobs -> product:tracing, score=133)
ddtrace.internal.ci_visibility.filters -×-> ddtrace.trace  (product:ci_visibility -> product:tracing, score=133)

To see all violations, download the layers-base.json and layers-pr.json artifacts from this CI job and run:

uv run --script scripts/import-analysis/layers.py compare layers-base.json layers-pr.json

[cit-pr-commenter-54b7da]

Codeowners resolved as

Resolved from the full PR diff against main using the target branch CODEOWNERS file.
CODEOWNERS team requests not listed below are not required by the current file set.

ddtrace/debugging/_debugger.py                                          @DataDog/debugger-python
ddtrace/debugging/_function/discovery.py                                @DataDog/debugger-python
ddtrace/debugging/_probe/model.py                                       @DataDog/debugger-python
releasenotes/notes/fix-di-line-probe-method-declaration-e13fdd953806edc3.yaml  @DataDog/apm-python
tests/debugging/function/test_discovery.py                              @DataDog/debugger-python
tests/debugging/test_debugger.py                                        @DataDog/debugger-python