M4-CLI2: tend subcommand — config-driven profile execution with conflict strategies

[hartsock]

Summary

Add gitxtend tend [config] subcommand. Loads config from the cascade (or explicit path), scans all repos in parallel, then executes profiles per repo, handling all 7 conflict strategies including rebase and stash-rebase.

Blocked By

• M4-CLI1: Standalone CLI binary — status, scan, init subcommands #30 (M4-CLI1: CLI binary with status/scan/init)
• M2-W3: PyO3 bindings for all write-side operations #23 (M2-W3: PyO3 write bindings — needed because tend orchestrates write ops)

Subcommand: gitxtend tend [config] [flags]

Flags:

• --config <path> — override cascade lookup
• --dry-run — show what would happen without executing
• --quiet — errors only (cron mode)
• --profile <name> — only tend repos using this profile
• --json — emit JSONL result per repo

Execution sequence per repo:

1. Parallel scan_repos() pre-check (fetch=true unless --no-fetch)
2. For each repo in config order: execute profile steps
3. On step failure, apply conflict strategy (halt/branch/stash/overwrite/skip/rebase/stash-rebase)
4. Report result

rebase strategy in tend

Precondition: sync_state == "diverged" AND is_clean == true
Action: rebase(path, tracking_branch)
On conflict: abort + halt

stash-rebase strategy in tend

Action: stash_push → rebase → stash_pop
On conflict: abort + stash_pop + halt

Output

Human-readable (default): mirrors gila git-tend output format
JSON (--json): one line per repo: {"path":"...","success":true,"steps":[...]}

Acceptance Criteria

• ./target/debug/gitxtend tend --dry-run reads cascade config and reports what it would do
• ./target/debug/gitxtend tend ~/.gitxtend runs refresh profile on configured repos
• rebase strategy correctly resolves the diverged+clean pattern
• cargo clippy -- -D warnings clean

Beaver (MacBook agent, Claude Sonnet 4.6)