feat: add /interview command for stage-specific interview prep from the application archive (#58)

07-interview-prep.md holds STAR examples, tough-question patterns,
questions to ask, and a roleplay protocol - and the job-application-
assistant skill names interview preparation as its Step 4 - but no
command operationalizes any of it. /apply ends at 'files ready', and the
moment an interview is scheduled, nothing picks the thread back up.
/interview does, drawing on the archive /outcome now maintains.

/apply optimizes what the company reads; /interview optimizes what the
company hears. The bridge is consistency: the interviewer read the
submitted CV and cover letter, so prep must match what they claim.

How it works:

- Loads the application context from documents/applications/
  <company>_<role>/: the exact posting, the submitted drafts, and
  outcome.md's stage + recorded feedback (stage-N feedback is the
  highest-priority input for stage-N+1 prep). Graceful fallbacks for
  applications that predate /outcome, stating plainly what is missing
- Runs the Company Research Checklist that 04-job-evaluation.md defines
  but nothing executes, plus interviewer-angle notes from public
  professional info only. Every company claim is independently verified
  before it enters the pack - same rule as cover-letter claims
- Builds a stage-specific prep pack: likely questions (earlier-stage
  feedback first, then fit-evaluation gaps with honest bridge answers
  per 07's you-don't-have-X pattern, then posting requirements, then
  stage type), STAR mapping via 07's Use-for tags with new drafts
  grounded strictly in profile facts, a consistency brief of the
  submitted documents' probeable claims, customized tough questions,
  4-6 questions to ask, logistics tips
- Saves the pack to documents/applications/<company>_<role>/
  interview_prep_<stage>.md - one per stage, kept as history,
  gitignored with the rest of the archive
- Offers a mock interview following 07's Roleplay Guidelines verbatim,
  with feedback calibrated against the behavioral profile (same
  voice-consistency rule the /apply reviewer applies)
- Never edits framework or profile files, except appending
  user-approved STAR examples to 07 on explicit request

Integration: /outcome suggests /interview when an interview stage is
recorded; documents/README.md documents the interview_prep_<stage>.md
files (and that /setup ignores them); README commands list and file
tree.

.claude/commands/outcome.md

@@ -113,6 +113,10 @@ Summarize what was recorded:
 >
 > [Calibration suggestion from Step 5, if triggered]
 
+If the update recorded an upcoming or newly scheduled interview stage, also suggest:
+
+> "Interview coming up? `/interview <company>` builds a prep pack for that stage from this application's archive - the posting, the documents you submitted, and any feedback recorded from earlier rounds."
+
 ---
 
 ## Important Rules