Document the `--instruction-policy auto` import behavior

[kelos-bot]

kanon import --help advertises --instruction-policy auto, but the README only documents codex, claude, merge, and skip.

I reproduced this in a fresh home: the help text says auto is a valid option, but the onboarding docs never explain what it does or when it differs from the other policies.

Implementation-wise, auto is the default and it:

• uses Codex instructions when only ~/.codex/AGENTS.md exists
• uses Claude instructions when only ~/.claude/CLAUDE.md exists, or when both files match
• errors when both files exist and differ, telling the user to rerun with codex, claude, merge, or skip

Suggested fix: add a short auto description to the README import section and keep the help text/README wording aligned.

[kelos-bot]

🤖 Kelos Task Status

Task kanon-triage-issues-9cc3b4b90532 has succeeded. ✅

[kelos-bot]

🤖 Kelos Agent @gjkim42

Kanon Triage Report

Kind: kind/docs
Priority: priority/important-longterm — Documentation mismatch is user-facing but low risk and does not block the import command from working.
Actor: actor/kelos — The requested README/help wording alignment is concrete, scoped, and objectively verifiable.

Status: STILL VALID

Evidence:

• No merged PRs referencing Document the --instruction-policy auto import behavior #93 were found via gh pr list --state merged --search "93".
• No recent commits in the last 50 matched issue Document the --instruction-policy auto import behavior #93 or the instruction-policy auto documentation keywords.
• The CLI still advertises auto for import instruction handling in internal/cli/root.go.
• auto is still the default and a valid policy in internal/core/import.go and internal/core/import.go.
• The current auto branch still chooses an available instruction file or errors when Codex and Claude instructions differ in internal/core/import_assets.go.
• The README import section still only tells users to rerun with codex, claude, merge, or skip when files differ, without explaining the default auto policy in README.md.

Duplicates found: None found

Recommendation: KEEP OPEN