Part 2: add parametric algorithms to unified platform

[Siel]

This is part 2 of the split of #260 and is stacked on #264.

Scope:

• add the parametric API surface
• add the parametric runtime and algorithm implementation
• add parametric reporting, outputs, tests, validation assets, and the SAEM example

Why:

• keep the structural rewrite review separate from the parametric algorithm review
• preserve the unified-platform base as a small prerequisite for the parametric work

Validation:

• cargo check --tests --examples

[github-actions]

Bencher Report

Branch	split/unified-platform-parametric-pr
Testbed	mhovd-pgx

⚠️ WARNING: No Threshold found!

Without a Threshold, no Alerts will ever be generated.

• Latency (nanoseconds (ns))

Click here to create a new Threshold
For more information, see the Threshold documentation.
To only post results if a Threshold exists, set the --ci-only-thresholds flag.

Click to view all benchmark results

Benchmark	Latency	milliseconds (ms)
bimodal_ke_npag	📈 view plot ⚠️ NO THRESHOLD	4,945.90 ms
bimodal_ke_npod	📈 view plot ⚠️ NO THRESHOLD	1,349.50 ms
bimodal_ke_postprob	📈 view plot ⚠️ NO THRESHOLD	462.32 ms

🐰 View full continuous benchmarking report in Bencher