Add tests for rootdepth_main & soilfluxes !freedrain; fix 3 source bugs in RootDepth.jl

[Copilot]

Previously untested: rootdepth_main (entirely) and the !freedrain branch of soilfluxes. Running these paths exposed three bugs in RootDepth.jl that caused runtime errors before any assertions could be checked.

Bugs fixed in RootDepth.jl

• freedrain type mismatch — soilfluxes expects freedrain::Bool but rootdepth_main passes freedrain::Int directly as a keyword arg; Julia does not auto-convert. Fixed with Bool(freedrain).
• Undefined isotope variables — Lines referencing transpo18step and updated_o18 (removed when isotope tracking was commented out from soilfluxes) caused UndefVarError on any active vegetation cell. Commented out.
• dθ scope bug — dθ was first assigned inside the for itime loop but read at line 260 outside it. Julia may not expose loop-internal variables in the enclosing scope. Fixed by pre-initializing dθ = zeros(Float64, nzg) before the loop.

Tests added

• test/test_rootdepth.jl — Four testsets: zero-landmask skip, water-body cell (veg=1), free-drain vegetation cell (veg=7), non-free-drain vegetation cell (veg=7). Exercises the full call chain including extraction, soilfluxes, and updatewtd_shallow.
• test/test_soil_fluxes.jl — Three new testsets for !freedrain: jwt≤2 branch (water table below all layers), jwt>3 branch (water table at a mid-layer), and a free vs. non-free-drain comparison verifying rech=0 for non-free-drain and rech<0 for free-drain (negative = downward drainage).

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[kongdd]

@copilot 1. rootdepth_main还未测试；2. soilfluxes中if !freedrain # 非自由排水这种情景还未测试。

[Copilot]

@copilot 1. rootdepth_main还未测试；2. soilfluxes中if !freedrain # 非自由排水这种情景还未测试。

Done in bf917a8:

1. rootdepth_main tests — added test/test_rootdepth.jl with four testsets: zero-landmask skip, water-body cell (veg=1), free-drain vegetation cell, and non-free-drain vegetation cell. Also fixed three bugs in RootDepth.jl that blocked active-cell execution (undefined transpo18step/updated_o18 variables; freedrain::Int → Bool mismatch in soilfluxes call).

2. !freedrain (非自由排水) tests — added three new testsets in test_soil_fluxes.jl: jwt≤2 branch (water table below all layers), jwt>3 branch (water table in a middle layer), and a free vs non-free-drain comparison verifying that rech=0.0 for non-free-drain and rech<0 for free-drain (downward drainage sign convention).

[Copilot]

Pull request overview

该 PR 旨在为此前未覆盖的 rootdepth_main 全流程与 soilfluxes 的 !freedrain 分支补齐测试，并在测试驱动下修复若干会导致运行时报错的实现问题，从而提高 RootDepth/SoilFluxes 相关模块的稳定性与可回归性。

Changes:

• 修复 RootDepth.jl 中 soilfluxes 的 freedrain 关键字参数类型不匹配、以及循环外读取 dθ 的作用域问题，并移除/注释已删除的同位素相关变量引用。
• 修复 SoilFluxes.jl 在部分边界条件下未显式设置 k=2 三对角系数、以及干燥限制中 θ_cp 字段引用错误。
• 新增/扩展测试用例，覆盖 extraction、updatewtd_shallow、soilfluxes(!freedrain) 与 rootdepth_main 的关键路径，并更新总测试入口与 wtable 子测试入口。

Reviewed changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
src/RootDepth.jl	修复 freedrain 传参类型、dθ 作用域与同位素残留引用导致的运行时错误。
src/SoilFluxes.jl	补齐 k=2 系数设置以覆盖循环起点缺口；修正干燥限制中 θ_cp 取值字段。
src/extraction.jl	修复向量 clamp 广播用法；避免 rootfc==0 时的除零风险。
test/runtests.jl	将新增测试文件纳入总测试入口。
test/test_soil_parameters.jl	按当前土壤参数结构体字段更新断言，并补充全土壤类型的基本合法性检查。
test/test_soil_fluxes.jl	重构并新增 !freedrain 分支覆盖及自由/非自由排水对比测试。
test/test_extraction.jl	新增 extraction 单元测试覆盖核心行为与边界情形。
test/test_updatewtd_shallow.jl	新增 find_jwt/updatewtd_shallow/cal_factor 的单元测试。
test/test_rootdepth.jl	新增 rootdepth_main 集成测试以覆盖全链路调用（含 !freedrain 集成）。
test/wtable/test-river.jl	补充 using ASAP, Test 以确保独立运行该测试文件。
test/wtable/runtests.jl	将新增的 river 测试纳入 wtable 测试入口。

[kongdd]

@copilot 修复上述review comments