refactor(workflow): move planning context to FlickNote

[birdmanmandbir]

Summary

• remove the entire ttal task command surface and the TUI completion heatmap
• remove Taskwarrior-only, project, and obsolete plan-review skills
• make FlickNote orientation and research notes the durable planning and research source of truth
• keep goal-impl user-invoked only; planning skills stop after returning the note
• reject fenced blocks across all skill Markdown and keep commands as plain lines
• update agent templates and docs for the reduced TTAL surface

Kept intentionally

• existing Taskwarrior-backed pipeline internals used by ttal go
• ttal remind add/list/delete, whose daemon storage still uses Taskwarrior

Verification

• go test ./...
• go build ./...
• golangci-lint run --new-from-rev=origin/main
• ./docs/node_modules/.bin/vitepress build docs
• git diff --check
• confirmed ttal task returns unknown command
• confirmed no fenced blocks remain under skills/

Size

• Tokei code LOC: 88,792 on origin/main to 85,682 on this branch
• 3,110 code LOC removed, or 3.50%