[ENH] DevelopmentConstant to natively accept Series, DataFrames, and Triangles #1483

Description

DevelopmentConstant currently expects patterns to be a dict or a callable. When benchmark patterns or selected link ratios are already in pd.Series, single-row/column pd.DataFrame, or Triangle objects (such as outputs from Development.ldf_ or external tabular tables), users have to manually unpack them into a python dict before passing them to DevelopmentConstant.

Is your feature request aligned with the scope of the package?

• Yes, absolutely!
• No, but it's still worth discussing.
• N/A (this request is not a codebase enhancement).

Describe the solution you'd like, or your current workaround.

Extend DevelopmentConstant(patterns=...) to natively accept:

• pd.Series indexed by development age
• 1-row or 1-column pd.DataFrame
• cl.Triangle (extracting the development vector from ddims)
• estimators with ldf_ or cdf_ attributes (extracting the pattern based on style)

Current workaround is manually converting arrays or Series via .to_dict() before initializing the estimator. Supporting these types directly reduces boilerplate and keeps pattern ingestion consistent across estimators.

Do you have any additional supporting notes?

Originated during the review of PR #1473 from @henrydingliu's suggestion on pattern inputs: #1473 (comment)

Would you be willing to contribute this ticket?

• Yes, absolutely!
• Yes, but I would like some help.
• No.