Add normalize_recipe skill

normalize_recipe v1 turns a recipe page's title, raw ingredient lines,
steps and JSON-LD times into {ingredients: [{name, qty, unit, note}],
method, difficulty, minutes_total}. skills.NormalizeRecipe always runs it
at temperature 0. Validation requires one named ingredient per input line,
in order, so a mismatch gets the harness's repair turn. Code-derived
values win over the model's: JSON-LD total minutes, crockpot for a slow
cooker or crock pot mention, and a derived difficulty when the model gives
none. Golden tests with the Fake provider cover a typical recipe, a
repaired line-count mismatch, a slow-cooker recipe forced to crockpot and
JSON-LD minutes overriding the model.

Maestro task 9b4db226-9d8f-4251-a5de-adc45713c7bc

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/ai/skills/prompts/checksums.txt

@@ -2,3 +2,4 @@
 # A recorded line never changes. To change a prompt, bump the skill's
 # version, rename its template to match and add a line for the new version.
 echo v1 ab5d7884f5c7a2261c06b0c9353bb9597070c001420bd4cbb6ec6272c093fdce
+normalize_recipe v1 7174e5479fc020f3b2b39953d85411381aea26defb9943145e7864c5b752d7ee