Phase 2 tidy-up: revert intersphinx-qualified references once their target lectures are translated

During the 2026-07-18 Track B wave, seven resynced lectures referenced lectures that exist only in the English source. Per program decision (Matt, 2026-07-18), those {doc} references were qualified with the intermediate: intersphinx prefix so they resolve to python.quantecon.org until the targets are translated. When Phase 2 lands each target lecture here, the qualified references should revert to plain local refs — a routine translate forward resync of the referencing file will do this automatically, since the source uses local refs; this issue is the checklist to make sure none are forgotten.

One related non-doc case: ifp_egm.md's {eq}eqvfs`` (a label defined in the untranslated ifp_discrete.md upstream) was pointed at the local, mathematically-identical eqvfs_egm instead, since `{eq}` cannot cross projects. When ifp_discrete is translated, a resync will restore the upstream form. (The upstream source referencing the remote label while the local twin sits ten lines above the sentence looks like a source-side oddity — may be worth an upstream nit.)

Grep to audit at any time: grep -rn 'intermediate:' lectures/*.md

Start with the checklist in the issue and run grep -rn 'intermediate:' lectures/*.md to audit the listed lecture files. After the target lectures are translated, resync each referencing file with translate forward; done means the qualified references are restored to plain local references and the related eqvfs reference is restored by resync.