Replace built-in Tasks program template content

[edwin-zvs]

Summary

• Replaces the built-in "Tasks" Program template's markdown body with a lean dispatch rule (Todo -> In progress (dispatched) -> Done (merged)), pre-approving PR merges and requiring subagent archival once done.
• Template id/name ("tasks" / "Tasks") are unchanged — only the seeded markdown content changes.

New content

# Rule

Todo -> In progress (dispatched) -> Done (merged). I'm pre-approving all tasks pr to be merged, so you don't need to ask me. Each item, create claude subagent session to resolve. archive subagent sessions after done.

## Todo

## In Progress

## Done

Test plan

• cargo build succeeds in the worktree
• cargo test -p agentd passes (128 tests, including program_templates_use_filename_as_name_with_verbatim_markdown and program_templates_dir_override_redirects_reads)
• Verified new template markdown byte-for-byte via a standalone concat! check