feat(api): expose trend_analysis at top level (broken — listed in __all__ but unimportable)

[BnJam]

Problem

trend_analysis is listed in __all__ at python/eo_processor/__init__.py:151 and documented as a public top-level function in the README, but it is neither imported from ._core nor defined as a wrapper anywhere in __init__.py.

This means:

• from eo_processor import trend_analysis → ImportError
• from eo_processor import * → ImportError (star-import resolves every name in __all__, and trend_analysis is unbound)
• The README itself works around the bug by telling users to import from the private module: from eo_processor._core import trend_analysis

This directly violates the project's own invariant from skills/python-api-surface/SKILL.md: "if it's public, it must be importable, typed, tested, and documented."

The Rust kernel works

The function is fully implemented in src/trends.rs:20 and registered into _core at src/lib.rs:100. Only the Python public surface is broken.

Scope

File	Change
python/eo_processor/__init__.py	Add trend_analysis as _trend_analysis and TrendSegment as _TrendSegment to the from ._core import (...) block. Add a thin wrapper def trend_analysis(y, threshold): ... following the existing pattern (e.g. linear_regression at ~line 349).
python/eo_processor/__init__.pyi	Add stub for trend_analysis(y: Sequence[float], threshold: float) -> list[TrendSegment]: ... and a class TrendSegment matching the Rust struct fields (start_index, end_index, slope, intercept).
tests/test_trends.py	Add tests: no-break case (large threshold → single segment), a break case (linspace(0,10,50) + linspace(10,0,50) → ≥2 segments), invalid inputs (negative threshold, NaN in y).
README.md:321	Replace from eo_processor._core import trend_analysis with from eo_processor import trend_analysis.

Acceptance criteria

• from eo_processor import trend_analysis works
• from eo_processor import * works (no ImportError)
• Type stub present in __init__.pyi
• At least 3 tests covering the function
• README import example updated to use the public API
• ruff check python/eo_processor/ passes
• CI green

Version impact

Per the project's SemVer section: exposing a previously-unexported-but-documented function is a minor bump (new public surface, backward-compatible).

---

Note: A bump:minor label will be needed on the PR to trigger the automated version bump and release pipeline.

[BnJam]

Starting work on this issue. Plan: import trend_analysis/TrendSegment from _core into python/eo_processor/init.py, add a thin wrapper following the linear_regression pattern, add the type stub and TrendSegment class to init.pyi, add tests in tests/test_trends.py, and update the README import example to use the public API.

[BnJam]

Opened PR: #82

[BnJam]

technocore completed pipeline issue-handler.

Now let me look at the Rust implementation, the stub, tests, and README.
Now let me check the Sphinx docs and skills mentioned in the issue, plus how linear_regression is exposed.
Now let me check the environment for running tests.
No Python/Rust toolchain locally, so I'll rely on careful review + CI. Let me check CI and tox for what gates run.
Now let me implement. First, the import block in __init__.py:
Now add the wrapper near linear_regression (line 349):
Now the type stub __init__.pyi:
Now the tests in tests/test_trends.py:
Now the README fixes:
All private imports fixed. Let me verify the final state of the changed files:
Let me verify CoreError maps to ValueError in Python, since the tests rely on it:
Let me add a star-import regression test, which directly validates acceptance criterion #2:
Now let me review final state of all changed files and check for any other references:
All changes complete. Now create the branch, commit, and push:
PR created. Now add the bump:minor label and post the PR URL on the issue:
Done. PR: #82

Fix summary:

• python/eo_processor/__init__.py: imported trend_analysis as _trend_analysis and TrendSegment as _TrendSegment from ._core, added the thin trend_analysis(y, threshold) wrapper (mirroring linear_regression at __init__.py:349) and a TrendSegment = _TrendSegment alias. This binds the name in __all__ (line 151), fixing both from eo_processor import trend_analysis and star-imports.
• __init__.pyi: added class TrendSegment (start_index, end_index, slope, intercept) and the trend_analysis(y: Sequence[float], threshold: float) -> list[TrendSegment] stub.
• tests/test_trends.py: 5 tests — no-break single segment, break detection (≥2 segments), negative threshold rejection, NaN rejection, and a star-import regression test.
• README.md + docs/source/README.md: replaced the eo_processor._core workaround with the public import.

No local Python/Rust toolchain exists in this environment, so I couldn't run ruff/pytest locally; CI (tox lint + py tests) will verify. Added the bump:minor label to the PR to trigger the automated version bump/release.