feat(routines): human-readable cron schedule summaries in web UI

[G7CNF]

Summary

• add describe_cron() in src/agent/routine.rs for common routine cron patterns (with safe fallback)
• expose trigger_raw and human-readable trigger_summary in routine list/detail payloads
• update routines list UI to show raw cron as tooltip (title) while displaying readable summary
• update routine detail UI to show readable cron summary prominently, with raw schedule + timezone as secondary detail
• keep JSON trigger dump fallback for non-cron trigger types

Coverage

describe_cron() now covers common patterns including:

• every N minutes / hours
• daily schedules (including midnight)
• weekdays schedules
• single weekday schedules
• monthly day-of-month schedules
• 5/6/7-field cron inputs
• timezone suffix in output when present
• fallback for malformed/complex cron expressions

Closes #1131

Validation

• cargo fmt --all
• cargo test -p ironclaw test_describe_cron_common_patterns -- --nocapture
• cargo test -p ironclaw test_describe_cron_edge_cases -- --nocapture
• cargo clippy -p ironclaw --all-targets -- -D warnings

[gemini-code-assist]

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[G7CNF]

Status check: all required CI checks are green and there are no open review threads to address on this branch. Remaining blocker appears to be maintainer review/approval.

[zmanian]

Review: Human-readable cron schedule descriptions in web UI

Well-implemented feature. describe_cron() converts common cron patterns to plain English with clean fallback to raw expression.

Positives:

• Handles 5/6/7-field cron expressions
• Covers common patterns: minute/hour steps, daily, weekdays, specific weekday, monthly
• Ordinal formatting handles edge cases (11th, 12th, 13th)
• Timezone suffix when provided
• Falls back to cron: <raw> for unrecognized patterns
• Web UI shows human-readable as primary text, raw cron in tooltip
• trigger_raw and trigger_summary added to both list and detail API responses
• Good test coverage for common patterns and edge cases

LGTM.