use doctest ELLIPSIS for bandwidth() values to avoid ULP failures

bandwidth() gets its value from a scipy.optimize.root_scalar bisection,
so the last digit or two of the repr differs across scipy/BLAS builds.
The full-precision literals matched locally but failed on GitHub.

Truncate to ~14 significant digits with # doctest: +ELLIPSIS.  This
keeps the examples verified (unlike +SKIP, used elsewhere in the repo
for platform-dependent output), and trim_doctest_flags (on by default)
strips the flag comment from the rendered HTML.

Also applied to the G1*G2 example, which has the same origin and had
not failed yet.

Verified with "make doctest" in doc/: 728 tests, 0 failures.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Author: murrayrm

control/lti.py

@@ -706,15 +706,15 @@ def bandwidth(sys, dbdrop=-3):
     Examples
     --------
     >>> G = ct.tf([1], [1, 1])
-    >>> ct.bandwidth(G)
-    np.float64(0.9976283451102316)
+    >>> ct.bandwidth(G)                     # doctest: +ELLIPSIS
+    np.float64(0.99762834511023...)
 
     >>> G1 = ct.tf(0.1, [1, 0.1])
     >>> wn2 = 1
     >>> zeta2 = 0.001
     >>> G2 = ct.tf(wn2**2, [1, 2*zeta2*wn2, wn2**2])
-    >>> ct.bandwidth(G1*G2)
-    np.float64(0.10184838823897456)
+    >>> ct.bandwidth(G1*G2)                 # doctest: +ELLIPSIS
+    np.float64(0.10184838823897...)
 
     """
     if not isinstance(sys, LTI):

doc/intro.rst

@@ -190,5 +190,5 @@ This documentation has a number of notional conventions and functionality:
   .. doctest::
 
      >>> sys = ct.tf([1], [1, 0.5, 1])
-     >>> ct.bandwidth(sys)
-     np.float64(1.4839084518312828)
+     >>> ct.bandwidth(sys)               # doctest: +ELLIPSIS
+     np.float64(1.4839084518312...)