docs(archive): ten completed tasks from the 09-05/06 session

Written as long-form learning rather than a list, per the archive's own
convention — these are blog and video source material, and the learnings are
the half worth keeping.

The through-line of the session, visible only once the entries sit together:
five separate failures where a CHECK was the broken thing, not the system it
watched. The delete verifier reporting 0/14 for fourteen successful deletions.
Six test suites green because they ran nothing. An assertion with an
always-true escape clause. A drift guard that had been failing behind an
--ignore flag people were trained to pass. A subagent's ten red tests that were
its own stale checkout.

Nearly committed this append on the wrong base: the shared checkout is on an
older branch whose copy of this file is 162 lines behind master, so appending
there and committing would have DELETED master's most recent entries. Extracted
the block, restored the shared tree byte-identical, re-applied on origin/master
in a worktree. Same lesson as the rest of the session — a stale read makes an
append destructive, and the file being tracked is exactly what hides it.