fix: trim leading and trailing whitespace in output fields - #465

Fixes #15

LLM outputs often include leading/trailing whitespace and newlines. The formattedValue computed property in TextInput.vue already does .trim(), but it was only used for the copy button and the hasValue check -- the actual display still used the raw value prop.

This change uses formattedValue for the :model-value binding when isOutput is true, so output fields display trimmed text. Input fields are not affected.

Before (empty lines and leading spaces at top of output):

before

After (text starts immediately, no wasted space):

after