Add @Strategy marker annotation for static-polymorphism strategies

[dougqh]

What Does This Do

Adds @Strategy, a marker annotation for static-polymorphism strategy types and parameters — the stateless, concrete-typed policy objects the JIT can devirtualize and inline so one shared algorithm specializes to straight-line code per caller.

Why

First step toward making the *Hashtable / LightMap collections family a coherent, learnable set built on a single strategy grammar. Landing the marker first telegraphs the pattern ahead of the larger consistency changes, and gives a future checker (APT / Error Prone) a target to verify against.

Marker-only — no enforcement yet. The discipline it names is held by hand for now; the contract lives in the javadoc.

Design notes

• @Target({TYPE, PARAMETER}) — on a type: "this is a strategy" (hold it static final, concrete-typed, so it inlines). On a parameter: "this is a strategy slot" (the arg should be a static final constant or a non-capturing lambda). The parameter target lets us tag a slot even when its type can't be (e.g. a java.util.function.Function we don't own).
• @Retention(SOURCE) — zero bytecode footprint, no runtime metadata (agent hygiene); a source-level checker reads it fine.
• @Documented — the contract is human-facing, so it belongs in the generated javadoc.
• @Inherited — documentary intent (a concrete subclass of a strategy base is a strategy); inert under SOURCE retention, kept as a signal.

Applications

None here, by design — the first uses land in the stacked FlatHashtable PR that builds on this one.

🤖 Generated with Claude Code

[datadog-datadog-prod-us1-2]

🎯 Code Coverage (details)
• Patch Coverage: 100.00%
• Overall Coverage: 57.27% (+0.00%)

_{This comment will be updated automatically if new data arrives.
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[dd-octo-sts]

🟢 Java Benchmark SLOs — All performance SLOs passed

Suite	Status
Startup	🟢 pass

SLO thresholds are defined here based on automatically generated metrics. A warning is raised when results are within 5% of the threshold.

PR vs. master results

Scenario	Candidate	master	Δ (95% CI of mean)
startup:insecure-bank:iast:Agent	13.94 s	13.92 s	[-0.6%; +0.8%] (no difference)
startup:insecure-bank:tracing:Agent	12.90 s	13.01 s	[-1.6%; -0.1%] (maybe better)
startup:petclinic:appsec:Agent	16.95 s	16.67 s	[+0.7%; +2.7%] (maybe worse)
startup:petclinic:iast:Agent	16.90 s	16.87 s	[-0.4%; +0.8%] (no difference)
startup:petclinic:profiling:Agent	16.83 s	16.87 s	[-1.4%; +0.9%] (no difference)
startup:petclinic:sca:Agent	16.94 s	16.61 s	[+0.9%; +3.2%] (maybe worse)
startup:petclinic:tracing:Agent	15.66 s	15.97 s	[-6.1%; +2.3%] (no difference)

Commit: da649614 · CI Pipeline · Benchmarking Platform UI

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