CN allocation tech notes improvements

[huiqi-wang]

Description of changes

Specific notes

Contributors other than yourself, if any:

CTSM issues resolved or otherwise addressed, if any:
Resolves #3866

• references related:
  Line 14, 16: Plant Respiration → Chapter :numref:rst_Plant RespirationLine 14: Sprugel → :ref:Sprugel et al. (1995)
  Line 72: Larcher → :ref:Larcher (1995) Line 81: Allen / Vanninen / Axelsson — all three are now :ref: Lines 72, 161: Table → :numref:Table Allocation and CN ratio parameters
  Lines 163, 182: Equations → :eq:19.7, :eq:19.9, :eq:19.10, :eq:19.11, :eq:19.12 Lines 259, 335: FUN → Chapter :numref:rst_FUN

• Bug fixes:
  Line 72: g_l → g_1 (typo)
  Line 79: parentheses fixed in the a_3 sigmoid → \frac{2.7}{1 + e^{-0.004 (NPP_{ann} - 300)}} - 0.4
  Line 111: missing table row separator inserted (BDS boreal / C₃ arctic grass)
  Line 194: CF_{alloc,leaf} → CF_{alloc,leaf_tot} (consistent with Eq. 19.14–19.25)

• add more explanation and clarification:
  Line 45: 86400 is now explained (s day⁻¹, converts τ from days to s)
  Line 147: PFT abbreviation legend (NET/NDT/BET/BDT/BES/BDS + R/I)
  Lines 64–70 & 154–159: Eqs. 19.7 and 19.9 use \begin{aligned} + \text{}
  Line 256: section title capitalized "Nitrogen Allocation"
  Line 85: table title "carbon:nitrogen" (not :)
  Line 88: Target :math:CN_{...}`` (text outside math) — keep it consistant with similar item in CN Pools

- flag some but have not solved yet

1. Eq. 19.26 (min(demand, supply)) and Eq. 19.40 (N_uptake · demand_i / demand_tot) both define NF_{alloc,i}. This is confusing to me. I feel like there some sentences missing here, such as when When N_{uptake} ≥ NF_{demand,tot}, then xxxx, need help from science team.
2. The table shows 9-column in rst file but shows 7 columns in html. It may truncate in PDF; verify after a new html build, then decide split/landscape if needed

[wwieder]

@slevis-lmwg do you mind reviewing this?

[slevis-lmwg]

@huiqi-wang thank you for your work in this PR!

• Good news, the table looks fine in the html because it has a scroll bar at the bottom.
• I requested two updates that I will try to push to the PR myself.
• Then I will merge this to b4b-dev.

[slevis-lmwg]

I messed up the table. Fixing now.

[slevis-lmwg]

Looks good to me. Thanks again @huiqi-wang.

[huiqi-wang]

Thank you for your help too!!