Add --hook-* CLI flags to override agent hooks from the command line

[dgageot]

Summary

Add five new repeatable CLI flags that let users attach lifecycle hooks to any agent without modifying its YAML config:

• --hook-pre-tool-use <cmd> — runs before every tool call
• --hook-post-tool-use <cmd> — runs after every tool call
• --hook-session-start <cmd> — runs when a session starts
• --hook-session-end <cmd> — runs when a session ends
• --hook-on-user-input <cmd> — runs when waiting for user input

Example

docker agent run agent.yaml \
  --hook-pre-tool-use "./scripts/validate.sh" \
  --hook-post-tool-use "./scripts/log.sh" \
  --hook-session-start "./scripts/setup-env.sh"

Details

• CLI hooks are appended to any hooks already defined in the agent's YAML config (they don't replace them)
• Pre/post-tool-use hooks added via CLI match all tools (equivalent to matcher: "*")
• Empty/whitespace-only commands are silently skipped
• All flags are repeatable: pass multiple to register multiple hooks

Changes

• pkg/config/runtime.go — Add hook string-slice fields to Config; update Clone()
• pkg/config/hooks.go (new) — HooksFromCLI(), MergeHooks(), and CLIHooks() helpers
• pkg/config/hooks_test.go (new) — Comprehensive tests including empty-command filtering, merge semantics, clone isolation
• cmd/root/flags.go — Register the five --hook-* flags
• pkg/teamloader/teamloader.go — Merge CLI hooks into agent config at load time (hoisted before loop)
• docs/features/cli/index.md — Document new flags in CLI reference
• docs/configuration/hooks/index.md — Add CLI Flags section to hooks docs

[docker-agent]

Review Summary

Assessment: 🟢 APPROVE

This PR cleanly implements CLI flags for attaching lifecycle hooks to agents without modifying YAML config. The implementation is well-structured with proper testing and documentation.

Code Quality

✅ Hook merging logic — Correctly appends CLI hooks to config hooks without mutation
✅ Empty command filtering — Properly skips whitespace-only commands
✅ Clone implementation — New hook fields properly cloned with slices.Clone()
✅ Integration point — CLI hooks merged at the right place in teamloader
✅ Test coverage — Comprehensive tests for all edge cases (empty commands, merging, isolation)
✅ Documentation — Both CLI reference and hooks docs updated with examples

Findings

No issues found in the changed code. The implementation follows Go best practices and handles edge cases correctly.

Note: During review, a pre-existing nil pointer dereference was identified in pkg/config/runtime.go line 40 (DefaultModel.Clone() when DefaultModel is nil). This is outside the scope of this PR but may warrant a separate fix.

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Review completed by docker-agent PR reviewer