docs(research): clarify research() returns daily rows, not hourly obs (#52)

[helloiamvu]

Summary

Addresses #52. A user asked why research() returns daily means and how to access hourly station observations. Clarify in the Returns docstring that research() yields one daily settlement-summary row per date (obs_* are settlement-window aggregates), not sub-daily rows.

Changes

• research() Returns section: explicitly states the daily granularity, that research() does not return raw hourly rows, points to weather.obs() (also daily) for obs-only frames, and notes sub-daily / raw_metar access is a Sprint 0.5+ item (raw METARs preserved internally for the planned re-parse workflow).

Docs-only; no code behavior change.

Review

Codex (gpt-5.5, medium) — clean, no findings.

TS Parity

N/A — docstring-only clarification, no API surface change.

[github-actions]

📝 Docs-required check: REMINDER

API-surface change without docs and no opt-out — surfacing reminder.

API-surface files changed:

packages/core/src/mostlyright/research.py

Docs files changed:

(none)

Docs surfaces to consider

• CHANGELOG.md — every behavior change goes here. Auto-synced to the docs site on every release.
• docs/ — hand-authored prose. Lifted into the landing repo as MDX on every release.
• Per-package READMEs (packages/*/README.md, packages-ts/*/README.md) — front-door copy on PyPI / npm.
• Docstrings (Python """ ... """ / TypeScript JSDoc /** ... */) — propagate to the auto-generated API reference via Sphinx / TypeDoc.

How to silence this reminder

• Add a docs change to this PR (any *.md / *.mdx under docs/, or CHANGELOG.md, or any README.md).
• Apply the docs-not-required label.
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This check is advisory — it never blocks the merge.

[github-actions]

Parity ticket gate: FAILED

Parity-ticket gate FAILED.

This PR touches the parity-trigger surface (python side) and
does NOT include a paired TypeScript change, a `Parity-Ticket: #<num>` reference, or a
`python_only: true` justification.

Add ONE of the following to the PR body:

Parity-Ticket: #123
or
python_only: true — interim shim for mostly-light migration

Trigger-matching files in this diff:
  - packages/core/src/mostlyright/research.py

See `.planning/CROSS-SDK-SYNC.md` §2 for the full workflow and
`.github/parity-trigger-paths.json` for the surface definition.
::error::Parity-ticket gate FAILED.

See CROSS-SDK-SYNC.md §2 for the workflow.