cmd: invoke reads --file data from disk twice (redundant I/O)

Description

When --file is passed to func invoke, the file contents are read from disk twice:

1. In newInvokeConfig() (line 280-286) — reads file into cfg.Data
2. In runInvoke() (line 201-207) — reads the same file again into m.Data

The second read is redundant because m.Data is already initialized from cfg.Data at line 195, which already contains the file contents from the first read. The second read at line 206 just overwrites m.Data with identical content.

Impact

• Wasted I/O (file read twice for every invocation with --file)
• TOCTOU consistency risk: if the file changes between the two reads, the behavior would be unpredictable

Proposed Fix

Remove the second os.ReadFile block in runInvoke() (lines 200-207). The file is already read into cfg.Data during config creation.

/kind cleanup