kernel-cases: thread fit cases say what they grade

2969's description named another product's behaviour; 1443's and 2152's
still described the refusal. Each now says the hole is drawn at the
thread's nominal size and gets the fitted thread.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/kernel-cases/threads/1443-m5x0.7-thread-in-5mm-hole/expected.json

@@ -3,7 +3,7 @@
   "tangency-labs/solidcraft#1443",
   "tangency-labs/solidcraft#3060"
  ],
- "what": "a modelled M5x0.7 thread in a 5 mm hole (refused: it would cut 0.00 mm of the thread's depth)",
+ "what": "a modelled M5x0.7 thread in a 5 mm hole drawn at the thread's nominal size (was refused: it would cut 0.00 mm of the thread's depth)",
  "source": "analytic",
  "method": "ISO 68-1 basic profile: H = P sqrt3/2, basic depth 5H/8. External groove (the space between teeth): a trapezoid P/4 wide at the root radius d/2 - 5H/8, widening by 2 tan30 per unit of radius to 7P/8 at d/2. Internal groove: P/8 wide at the major radius d/2, widening to 3P/4 at the minor radius, cut only where there is material (r >= hole radius). Pappus: volume per turn = 2 pi A rc (A the trapezoid area, rc its centroid radius from the axis); a helical sweep of L/P turns removes exactly (L/P) x that, where each end of the thread is a free end or lies inside material. A 5 mm hole through a D14 x 4.2 disc, drawn at the thread's nominal size, takes a modelled M5x0.7: the hole is first filled to the tap drill (major - pitch = 4.3 mm, rho=2.15), then the groove is cut, the same thread as in a hole drilled at the tap drill. Whole length, both ends free (6 turns): V = pi 7^2 4.2 - pi 2.15^2 4.2 - 6 x V_turn(clipped at rho) = 646.5398 - 60.9925 - 6 x 1.45465 = 576.8194 mm3. The thin lips a tap leaves at each end are below 0.2% of the volume. Tolerance 1%: a modelled thread is a faceted helical solid (radial chord error up to 1% of the pitch on every wall, i.e. a volume deficit of about 4/3 x sag/R).",
  "outcome": "solid",

tests/kernel-cases/threads/2152-m3x0.2-thread-in-3mm-hole/expected.json

@@ -2,7 +2,7 @@
  "sources": [
   "tangency-labs/solidcraft#2152"
  ],
- "what": "a modelled M3x0.2 thread in a 3 mm hole (the same refusal as a hole at the nominal size)",
+ "what": "a modelled M3x0.2 thread in a 3 mm hole drawn at the thread's nominal size (was refused like any hole at the nominal size)",
  "source": "analytic",
  "method": "ISO 68-1 basic profile: H = P sqrt3/2, basic depth 5H/8. External groove (the space between teeth): a trapezoid P/4 wide at the root radius d/2 - 5H/8, widening by 2 tan30 per unit of radius to 7P/8 at d/2. Internal groove: P/8 wide at the major radius d/2, widening to 3P/4 at the minor radius, cut only where there is material (r >= hole radius). Pappus: volume per turn = 2 pi A rc (A the trapezoid area, rc its centroid radius from the axis); a helical sweep of L/P turns removes exactly (L/P) x that, where each end of the thread is a free end or lies inside material. A 3 mm hole through a D10 x 2 disc, drawn at the thread's nominal size, takes a modelled M3x0.2: the hole is first filled to the tap drill (major - pitch = 2.8 mm, rho=1.4), then the groove is cut, the same thread as in a hole drilled at the tap drill. Whole length, both ends free (10 turns): V = pi 5^2 2 - pi 1.4^2 2 - 10 x V_turn(clipped at rho) = 157.0796 - 12.3150 - 10 x 0.07477 = 144.0169 mm3. The thin lips a tap leaves at each end are below 0.2% of the volume. Tolerance 1%: a modelled thread is a faceted helical solid (radial chord error up to 1% of the pitch on every wall, i.e. a volume deficit of about 4/3 x sag/R).",
  "outcome": "solid",

tests/kernel-cases/threads/2969-m48x0.75-thread-in-48mm-hole/expected.json

@@ -2,7 +2,7 @@
  "sources": [
   "tangency-labs/solidcraft#2969"
  ],
- "what": "a modelled M48x0.75 internal thread in a 48 mm hole (a workflow Fusion accepts)",
+ "what": "a modelled M48x0.75 internal thread in a 48 mm hole drawn at the thread's nominal size",
  "source": "analytic",
  "method": "ISO 68-1 basic profile: H = P sqrt3/2, basic depth 5H/8. External groove (the space between teeth): a trapezoid P/4 wide at the root radius d/2 - 5H/8, widening by 2 tan30 per unit of radius to 7P/8 at d/2. Internal groove: P/8 wide at the major radius d/2, widening to 3P/4 at the minor radius, cut only where there is material (r >= hole radius). Pappus: volume per turn = 2 pi A rc (A the trapezoid area, rc its centroid radius from the axis); a helical sweep of L/P turns removes exactly (L/P) x that, where each end of the thread is a free end or lies inside material. A 48 mm hole through a D54 x 3 disc, drawn at the thread's nominal size, takes a modelled M48x0.75: the hole is first filled to the tap drill (major - pitch = 47.25 mm, rho=23.625), then the groove is cut, the same thread as in a hole drilled at the tap drill. Whole length, both ends free (4 turns): V = pi 27^2 3 - pi 23.625^2 3 - 4 x V_turn(clipped at rho) = 6870.6631 - 5260.3515 - 4 x 17.37563 = 1540.8091 mm3. The thin lips a tap leaves at each end are below 0.2% of the volume. Tolerance 1%: a modelled thread is a faceted helical solid (radial chord error up to 1% of the pitch on every wall, i.e. a volume deficit of about 4/3 x sag/R).",
  "outcome": "solid",