Three of gig-up's four standing NO-GO blockers were one file and one buffering
bug. Cleared them, verified each by planting the failure back.

**something_about_drums.tidal — two typos, both silent by design of the tooling**

  :13  `(<| "~ <s s <s!3 ~> <~!7 [~ s]>>")d1` — a stray `d1` pasted straight
       after the closing paren, no operator, no newline. GHC reported it as
       "Variable not in scope: d1" at 13:56, and because a parse error takes the
       whole do-block with it, the reported line belonged to the GROUP, not to
       the break. The d2 block never ran.
  :81  `d8 $ gF1 $ gM1` — d8 copy-pasted from d1's block without updating the
       family macro. The authored map puts d8 in gM2 with d2 and d3, so d8 was
       wired to the wrong mute family: pressing d8's mute would have taken d1
       with it, live, and nothing about the code looked wrong.

  after: `silent-eval --seeded` OK (every declared orbit emits events),
  `fix-mute-roles --check` WOULD REWRITE: 0 lines, `pvlint (setlist)` ok.

**check-boot-blocks.py — the check was the third defect**

`tools/check-boot.sh` run alone passed clean, every line green, while gig-up
called the same check FAIL. The difference was not the rig. Under gig-up the
checker crashed:

    ValueError: invalid literal for int() with base 10: '6C1o'

`'6C1o'` is two output lines interleaved character-wise. The cause is in the
capture: stdout and stderr are deliberately ONE merged pipe (separate capture
would put every marker before every error and attribute each error to the last
block — the mis-attribution this tool exists to prevent), but GHC block-buffers
stdout while writing errors to stderr unbuffered. Two writers, one pipe, so a
marker could be flushed into a chunk a stderr write had already cut into. Rare
enough to look like a phantom, and it presented as "your boot helpers are
broken" — the rig's most alarming failure — when nothing was wrong.

  - `hSetBuffering stdout LineBuffering` is now the script's first statement, so
    each marker is one atomic write, in order.
  - Markers are self-delimiting (`@@PVBLOCK i start @@`) and matched by regex, so
    a torn one CANNOT parse as intact.
  - A torn marker, or a parse error that cannot be placed, is now INCONCLUSIVE
    (rc=2, "rerun") rather than a crash — and rather than a silent skip, which
    would have hidden a real error behind a green verdict.

Verified: 3 consecutive clean runs, then a planted unbalanced paren appended to
the block starting at :581 was caught and blamed on exactly that block
(rc=1, "block 16 (starts near bt.hs:581) is NOT one statement"). A checker that
cannot catch a planted bug is worth nothing, so that test is the one that counts.

gig-up: 4 blockers -> 2 (surface-grid migration debt, fader baseline).