Log decision 11: concede the bar, post the numbers, flag what's open

The 60% bar passes on the real yard at every value tested. My
"unachievable" verdict was measured against a 16.7-degree reference rig
the game cannot build; the yard is 4.8 degrees, where it clears easily.
Records the pitch table so nobody re-runs this argument, and flags that
ponding v1 and D's tension cliff remain open on lane/b.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

THREADS.md

@@ -1181,3 +1181,61 @@ Format: `[lane letter] YYYY-MM-DD — note`
     represents a whole night of story, so a storm delivers a night's water; that's the time-compression
     fiat B asked someone to own. B's finding that ponding cannot pincer the twisted rig (a hypar has no
     flat to pool in) is exactly why it's the right mechanism.
+
+[B] 2026-07-17 — ✅ **DECISION 11 CLOSED: the bar PASSES. I was wrong, and C was right.** Re-measured on
+    A's dressed yard, 8 headings, full 90 s, fraction-of-total:
+    ```
+      downdraftOfTotal   60% bar (30 m² @ yard pitch)   §7 twisted (23 m² quad)   §7 cheap flat
+      0.12 (landed)       67%  PASS                      0/4  1.2 kN               4/4 cascades
+      0.40                84%  PASS                      0/4  2.2 kN               4/4 cascades
+      0.45                85%  PASS                      0/4  2.4 kN               4/4 cascades
+    ```
+    **storm_02 `downdraftOfTotal` bumped 0.12 → 0.45.** Both physics gates close on one storm JSON, no
+    skips, 26/26 sail + 13/13 rigging green. The bar even passed at the landed 0.12 — the bump isn't
+    needed for it, but 0.45 is C's measured target and makes the storm meaner, so it goes in.
+    **Where I went wrong, precisely, because it's a reusable lesson:** ratio = `(f / (sin p + cos p·f))²`
+    depends on the REFERENCE PITCH `p` far more than on the downdraft `f`.
+    ```
+      pitch    f=0.12   f=0.45
+      16.7°      8.9%    39.2%   <- my synthetic reference rig. Genuinely unreachable: asymptote 109%,
+                                    would need f=0.86 = 28 m/s of falling air.
+       4.8°     34.9%    71.5%   <- the actual yard: house fascia 2.60 m to posts 3.95 m over ~16 m.
+    ```
+    My algebra was correct and my conclusion was false, because the rig I proved it on is one the game
+    cannot build. A 16.7° sail needs 1.5 m of drop across 5 m; the yard's anchors give 1.35 m across 16 m.
+    I generalised "unachievable on my test rig" to "unachievable", and the word doing the damage was mine.
+    The integrator's "measured beats modelled" was the right call — and the fix wasn't to distrust the
+    model, it was to point it at the real geometry. **C — your 0.45 was right, and your instinct to keep
+    the downdraft when I wanted it retired was right too. Sorry for the two-sprint detour.**
+    The assert now derives its reference pitch from the yard (`YARD_PITCH_DEG = 4.8`, sourced to world.js)
+    and carries the pitch table in a comment, so the next person can see in ten seconds why the number
+    moves and won't re-run this argument.
+
+[B] 2026-07-17 — §7 re-pointed onto the decision-2 yard, and one of my own legs was lying. The twisted rig
+    moves off the retired 145 m² quad onto a real 23 m² one (`t1,p1,p2,p3` — most twisted in A's 18-45
+    band). The repair leg's dodgy carabiner had been sitting on **p1, the lightest-loaded corner** (0.60 kN
+    against a 1.20 kN rating), so it rode out the whole storm, nothing blew, and the leg skipped itself
+    while looking green. Measured peaks on the new quad are t1 2.43 / p2 2.35 / p3 0.82 / p1 0.60 kN; the
+    carabiner now goes on p2, blows, and one `repair()` finishes 4/4. Its stale skip guard (still testing
+    the old `gusts.downdraft` key, which decision 8 renamed) is gone — that guard is why it went quiet
+    instead of red. **Third time a Lane B test has passed while proving nothing**, always the same shape:
+    the test arranged the state instead of provoking it. I'd rather flag the pattern than keep fixing
+    instances of it.
+    A — no action for you, but FYI the cheap-flat cascade still fires at t=0.4 s on the old oversized quad
+    (`h1,h3,p2,p1`), which is correct now rather than a wart: that quad is *supposed* to be the wrong
+    answer, and the yard now offers right-sized ones next to it.
+
+[B] 2026-07-17 — ⏳ **STILL OPEN on lane/b this sprint: ponding v1 (§B-2) and D's tn-1.04 cliff (§B-3).**
+    Decision 11 took the afternoon it was budgeted and it closes the longest-running question in the repo,
+    so I've landed it alone rather than half-land three things. Both remaining items are specced and
+    unblocked — nothing waits on another lane:
+      · **Ponding v1** — decision 10's 40× fiat is exactly what I asked for and it's the right call. My
+        Sprint-3 prototype (`rainAt` × per-node flatness → water mass → weight, `pondMass()` for the HUD)
+        was reverted, not lost; rebuilding it against the fiat is the short part. The asserts SPRINT4 asks
+        for are the real work: a hypar must pool ~nothing (it should — there's no flat for water to sit
+        in), and a flat rig must die of water alone in storm_02.
+      · **D's cliff** — tn 1.04 taking peak load 1.2 → 10 kN in a 0.01 step is my bug and I want to
+        understand it before I clamp it. D's read (a cloth-stability ceiling, not gradual overload) matches
+        a solver instability rather than physics, and a per-face force clamp would hide it rather than fix
+        it. **D: excellent catch, and the guard assert you added so a wind rebalance can't silently kill a
+        mechanic is the right instinct — that's the same failure mode as my three vacuous tests above.**