feat(config): add hapi.config and Catchment.from_yaml for YAML-driven runs

[MAfarrag]

Context

PR #214 replaced the hardcoded-Python-script workflow for configuring a Hapi run with a YAML
file plus a builder. This issue documents that change.

What Changed

• New module src/hapi/config.py: a pure pydantic schema (RunConfig and its nested blocks)
  that validates a parsed YAML mapping for both lumped and distributed runs. Imports nothing
  from hapi, so it stays a leaf of the import graph.
• New Catchment.from_yaml classmethod (src/hapi/catchment.py): reads the file, validates it,
  resolves every relative path against the file's own directory, and makes the read_* calls
  in the order the build-then-mutate pattern requires. Calibration.from_yaml returns its own
  type; Run.from_yaml is overridden to refuse, since Run holds entry points rather than
  being a catchment.
• New MeteoInputs.from_config (src/hapi/inputs.py): dispatches over meteo.source to the
  three existing loaders (from_rasters, from_netcdf, from_netcdf_files).
• Validation rules: required blocks per spatial_resolution and meteo.source, refusal of
  fields the chosen run shape will never read, routing_method derived from
  parameters.maxbas when unstated (and required to agree with it otherwise), the resolved
  meteorological window checked rather than two independent pairs, and every missing input
  path reported together before any reader runs.
• All four Coello example scripts (examples/hydrological-model/coello/run/) ported to
  YAML-driven configurations, each script paired with a .yaml file beside it.
• New docs page docs/examples/run-configuration.md, linked from the two existing run pages,
  plus the generated API reference docs/api/config.md.

Affected locations

File	Symbol
src/hapi/config.py	RunConfig, CatchmentConfig, MeteoConfig, FlowNetworkConfig, ParametersConfig, ConceptualModelConfig, GaugesConfig, OutputsConfig
src/hapi/catchment.py	Catchment.from_yaml
src/hapi/inputs.py	MeteoInputs.from_config
src/hapi/run.py	Run.from_yaml (override, refuses)

Usage Example

from hapi.catchment import Catchment
from hapi.run import Run

model = Catchment.from_yaml("coello-distributed-model-run-netcdf.yaml")
Run.RunHapi(model)

Verification

• hapi.config reaches 100% line and branch coverage
• Each YAML-built model verified field-for-field identical to the hardcoded assembly it
  replaces
• Two full /review-rounds passes (22 + 25 findings, all resolved) and a SonarCloud sweep
• docs/examples/run-configuration.md walks through a configuration end to end

Implemented in #214.