[Hackathon] Debug diagnostics for suppressed skill-nudge errors

[yuhaouno]

Summary

This is a narrow, independently reviewable subtask of #186 covering the two remaining src/lib/skill-nudge.ts silent catch paths.

The global --debug flag is not currently passed into the skill-nudge pre-action, so a failed profile lookup silently skips the nudge and an unreadable managed skill target is silently treated as absent. Those failures leave operators without a diagnostic even when they requested debug output.

Expected behavior

• With --debug, write an actionable diagnostic to stderr for each swallowed failure.
• Without --debug, preserve the existing warning text, output mode behavior, and exit status exactly.
• Never pollute JSON stdout or let a failing diagnostic sink break the command.

Scope

• Thread the parsed global debug flag into the pre-action nudge context.
• Add debug-only diagnostics for the profile-lookup and managed-target read failures.
• Add regression coverage for debug output and byte-identical non-debug behavior.

Relationship

Part of #186; deliberately split so this PR can close a concrete, scoped issue without closing the broader tracker.

[yuhaouno]

/assign

[testsprite-hob]

Assigned to @yuhaouno. Thanks for taking this on. (1 more slot available.)

Your open assigned issues (2/3):

• [Hackathon] Add structured debug logging to silent catch blocks #186 — [Hackathon] Add structured debug logging to silent catch blocks