v0.4.0-beta.3

Pre-release for community validation (#128 round 3). Ships the solar
generation leading-hole heal for installs that upgraded through beta.1:
those seeded their generation series from only the trailing rewindow, so the
older billing-period days were never fetched and Solar sold this period
undercounted the AGL app. This build re-imports the full window once to
backfill them. If you upgraded from beta.1 on a solar contract, please
confirm Solar sold this period and the Energy dashboard "Return to grid"
bars line up with the app after a poll cycle or two.

Fixed

• Solar generation: heal a leading hole in the generation statistics for
  contracts upgraded from beta.1 (#128). Beta.1 seeded the generation series
  from the consumption resume point, so on a caught-up install solar imported
  only the trailing REWINDOW_DAYS and the older billing-period days were never
  fetched — _resolve_fetch_start keys off the series' last row and never
  revisits them, permanently stranding (for the reporter) 24–27 June (~27 kWh)
  and making Solar sold this period undercount the AGL app. The coordinator
  now detects a leading hole (earliest stored row well after the backfill floor)
  and re-imports the full window in one contiguous batch via the existing hourly
  endpoint, so the cumulative chain is recomputed from a correct baseline. The
  heal is a one-time repair whose progress is recorded in the config entry
  (solar_heal = {state, floor, attempts}): the backfill floor is frozen
  when the heal starts so a rate-limited retry re-fetches the same window
  instead of sliding forward and dropping its oldest day; it stays pending —
  retrying — while any day was skipped (429 or a transient AGL error), up to a
  few attempts, then done and never re-runs, so an interrupted heal finishes
  and a permanently-erroring old day can't wedge it or re-sweep every poll.
  Bill-period solar totals are suppressed for a heal cycle (avoiding a transient
  over-read while the rewritten rows are still queued). Fresh installs and
  flat/ToU/non-solar contracts are unaffected.

Documentation

• Energy dashboard setup guide (docs/energy-dashboard.md): which
  haggle:… statistics to add per plan type (flat / ToU / solar), sensor
  glossary, data-timing expectations, and troubleshooting — including the
  "whole day as one bar on the wrong date" symptom caused by charting a
  sensor.… entity instead of a statistic (#137, also observed on #126).
• README refreshed: HACS default-store install (no more custom-repository
  steps), current status (ToU in validation, solar in beta), new Energy
  dashboard and Solar sections. info.md no longer tells users the
  cumulative Consumption sensor "fits the Grid consumption slot" — that
  instruction was the #137 footgun.

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