Custom chart indicators for /trading

Build an indicator for the charting terminal. It becomes a picker entry with a generated settings dialog, a legend row and saved-layout persistence, with no build step and no restart.

This is the chart (JavaScript) path. It has nothing to do with the Python openalgo.ta indicators used from strategies, scanners and backtests: different language, different runtime, different API. If the request is for a Python indicator, this skill is the wrong one.

The one rule

Never write a file into strategies/indicators/ directly. That folder is imported by the live chart, and the runtime fails silently in the ways that matter most: a column that is one element short, or a plot key that does not match what calc returns, draws nothing at all and raises nothing anywhere.

Always: write to a scratch path, validate, install on a pass.