fix: resolve code-review correctness bugs in README + build template

Three CONFIRMED defects, all from template/README text written before the
vo2max conflict section was revised, now reconciled with the corrected docs:

- README taper example said TSB '−5 to +5' (under-recovered) — corrected to
  the doctrinal +5 to +15 that periodization.md and both plan templates use.
- plan-template-build.md VO2 prescription said 'bias toward longer reps
  (3–5 min)... accumulate more time >90% VO2max than 30/30s' — contradicted
  its own cited source and was self-contradictory (140s ≠ 3–5 min). Replaced
  with the neutral menu: default medium (~2–4 min, near the ~140s optimum),
  short/long by goal, 'no rep length proven superior in cycling.'
- plan-template-build.md cited the phantom 'Yu et al.' (marked ❌ NOT FOUND in
  citations.md) — re-grounded the frequency heuristic in Seiler 2024.

DRY findings (inline PMID/DOI duplication, restated rhythm/field-test tables)
left as-is: inline citations and self-contained, independently-loadable docs
were explicit design requirements for this skill.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TqrhBhC3GEcKyaw8RTk8G6

assets/plan-template-build.md

@@ -25,8 +25,9 @@ carry more *intensity*, so recovery weeks matter more, not less.
 
 ## Weekly shape (build phase)
 
-Fewer but sharper hard sessions. **Frequency of hard sessions matters more than the exact
-polarized-vs-pyramidal label** (Yu et al. — see `references/periodization.md`). A common shape:
+Fewer but sharper hard sessions. **Getting enough quality hard sessions in tends to matter more
+than the exact polarized-vs-pyramidal label** — a heuristic grounded in Seiler 2024, not a
+quantified law (see `references/periodization.md`). A common shape:
 
 ```
 VO2max session:     1–2 × /week   (see references/vo2max-intervals.md for rep length / work:rest)
@@ -39,8 +40,9 @@ Recovery / off:     as needed
 
 ### VO2max prescription (from `references/vo2max-intervals.md`)
 - Goal is **maximizing time ≥90% VO2max**, not just "going hard."
-- Bias toward **longer reps (~3–5 min, ≈140 s optimum region)** at ~0.85 work:rest for rebuilding
-  sustained aerobic power; they accumulate more time >90% VO2max than 30/30s at matched intensity.
+- **No rep length is proven superior in cycling.** Default to **medium reps (~2–4 min, near the
+  pooled ~140 s optimum)** at ~0.85 work:rest; use short (30/15 s) or long (4–5 min) by athlete and
+  goal. Do not assume "longer is better" — see the modality conflict in `references/vo2max-intervals.md`.
 - Prescribe from **power**; for MTB, HR will lag and mislead (`references/data-confounds.md`).
 
 ## Keep durability alive