[ax] Deprecate --rules-summary, suggest --output-format=json

[TomasVotruba]

Why

--rules-summary prints a human-only table of "which rule applied how many times". The JSON output format already carries strictly richer per-rule data - every applied rule with its file and line (changes, added in #8448). For agents the table is redundant noise.

Current --rules-summary output:

Rules Summary
-------------

 * SomeRector was applied 3 times
 * OtherRector was applied 1 time

What

Deprecate --rules-summary without breaking it: when used, warn on stderr and point to the JSON format.

[WARNING] The "--rules-summary" option is deprecated and will be removed.
          Use "--output-format=json" instead, which reports every applied rule with its file and line.

• The option still works (summary still printed) - no behavior change, just a warning.
• Warning goes to stderr (getErrorStyle), so stdout / JSON stay clean.

Verification

• rector process --rules-summary -> warning on stderr, summary still shown, stdout clean.
• without the option -> no warning.

https://claude.ai/code/session_01HpU9jWfDU9D81fTTh1symd