docs: fix notation consistency in marginal model section

Use \mathbb{P} instead of \mathrm{Pr} to match the rest of the
document, and lowercase p_{L,i}, p_{R,i} in the likelihood
denominator to match the latent model convention.

Co-authored-by: Sam Abbott <contact@samabbott.co.uk>

Author: seabbs-bot

vignettes/model.Rmd

@@ -184,14 +184,14 @@ This approach uses the primary event censored distribution implemented in the [`
 
 Under the assumption that the forward distribution is shift-invariant (i.e. $f_x = f$ for all $x$), the double censoring probability from Section \@ref(interval-censoring) simplifies to
 $$
-\mathrm{Pr}(S_L < S < S_R \mid P_L < P < P_R) = \int_{P_L}^{P_R} g_P(x \mid P_L, P_R) \left[F(S_R - x) - F(S_L - x)\right] \text{d}x.
+\mathbb{P}(S_L < S < S_R \mid P_L < P < P_R) = \int_{P_L}^{P_R} g_P(x \mid P_L, P_R) \left[F(S_R - x) - F(S_L - x)\right] \text{d}x.
 $$
 For common delay and primary event distributions, such as gamma or lognormal delays with uniform primary events, `primarycensored` provides closed-form analytical solutions to this integral.
 For other combinations, numerical integration is used.
 
 Right truncation at time $T$ is handled by normalising the likelihood as in the latent model:
 $$
-\mathcal{L}(\mathbf{Y} \mid \mathbf{\theta}) = \prod_i \frac{\mathrm{Pr}(S_{L,i} < S_i < S_{R,i} \mid P_{L,i} < P_i < P_{R,i})}{\int_{P_{L,i}}^{P_{R,i}} g_P(z \mid P_{L,i}, P_{R,i}) F(T - z) \, \text{d}z}.
+\mathcal{L}(\mathbf{Y} \mid \mathbf{\theta}) = \prod_i \frac{\mathbb{P}(S_{L,i} < S_i < S_{R,i} \mid P_{L,i} < P_i < P_{R,i})}{\int_{P_{L,i}}^{P_{R,i}} g_P(z \mid p_{L,i}, p_{R,i}) F(T - z) \, \text{d}z}.
 $$
 
 Since no latent variables are required, identical observations can be aggregated and the likelihood computed once per unique combination of delay, censoring windows, and covariates.