feat: add fetch_latest_closed_rates_indexed and allow_whole_dollar_env opt-in (#45)

* feat: add fetch_latest_closed_rates_indexed and allow_whole_dollar_env opt-in (#43, #44)

Closes #43: add fetch_latest_closed_rates_indexed(client, *, symbol,
granularity, count) -> pd.DataFrame to mt5cli/trading.py. Internally
reuses fetch_latest_closed_rates_for_trading_client(), converts the
"time" column to a UTC-aware DatetimeIndex named "time", and drops the
original column. Exported from trading.__all__, mt5cli.__init__, and
STABLE_SDK_EXPORTS.

Closes #44: extend substitute_env_placeholders() with opt-in
allow_whole_dollar_env=False that expands whole-value $ENV_NAME strings
(entire string must be exactly $IDENTIFIER). Threaded through
build_config(), resolve_account_spec(), and resolve_account_specs() with
the same default=False. Partial strings like "plan$pass", "abc$ENV", or
"$ENV-suffix" are never expanded.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* chore: align Markdown table columns in docs and skill file

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* fix: treat numeric (float64) epoch seconds as UTC in _rate_time_to_utc

After DataFrame concat or NA upcast the time column becomes float64, which
is still epoch seconds. Using is_numeric_dtype instead of is_integer_dtype
fixes the silent misalignment. Using series.to_numpy() before passing to
pd.to_datetime avoids the redundant pd.DatetimeIndex() wrapper and aligns
with how existing rate-time normalization in schemas.py handles numeric
timestamps.

Add test_converts_float_epoch_seconds_to_utc_datetime_index to cover the
regression. Add a doc note clarifying that build_config cannot expand
login since that parameter is int | None.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* fix: reject NaT values after rate timestamp conversion in _rate_time_to_utc

pd.to_datetime() silently produces NaT for None/NaN inputs rather than
raising, so the function could return a DatetimeIndex containing NaT
despite documenting invalid timestamps as a ValueError. Check any(idx.isna())
after conversion and raise with a clear message.

Add test_raises_on_nat_time_column to cover the regression.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* Bump version to v0.9.0

* fix: handle object numeric rate timestamps

---------

Co-authored-by: Claude <noreply@anthropic.com>

pyproject.toml

@@ -1,6 +1,6 @@
 [project]
 name = "mt5cli"
-version = "0.8.3"
+version = "0.9.0"
 description = "Generic MT5 data and execution infrastructure for Python applications"
 authors = [{name = "dceoy", email = "dceoy@users.noreply.github.com"}]
 maintainers = [{name = "dceoy", email = "dceoy@users.noreply.github.com"}]