t27b: an anytype parameter the body reads with @TypeOf -- one instance per argument type (queen-public-agents.t27) #8713

Part of epic #8326 (coverage, see #6063). This is the last `type anytype` row in docs/reports/t27b_expectations.json.

Problem

In `specs/port/browseros/trios/agent-server/apps/server/src/api/routes/queen-public-agents.t27`, `heartbeatTime(value: anytype)` reads its parameter. It branches on `if (@typeof(value) == i64)` and returns `value` inside that branch. The tests call it with an i64, a string and null.

The reference passes 9/9. Zig compiles the function once per argument type, folds `@TypeOf(value) == i64` at compile time, and never type-checks a branch whose condition is false. The spec is correct; this is not a spec defect.

#8028 (any_param_plan) covers only an anytype parameter the body never reads, and any_param_plan.t27 lists this case as not covered.

Minimal repro

The reference gives 1/1 with 3 asserts. t27b refuses with `type anytype at line 3`.

module AnyTypeOfRepro;

fn h(v: anytype) -> ?i64 {
    if (@TypeOf(v) == i64) {
        return v;
    }
    return null;
}

test reads_by_type {
    assert(h(@as(i64, 5)) == 5);
    assert(h(null) == null);
    assert(h("x") == null);
}

What t27b needs

1. One instance of the function per distinct argument type at its call sites (monomorphization), named deterministically.
2. `@TypeOf(param) == T` folded per instance at compile time.
3. A branch whose condition folds to false is skipped, not lowered, as Zig skips analysing it.

Each decision belongs in a .t27 plan (any_param_plan), with net <= 0 hand-written lines (#8236). With `heartbeatTime` and its 4 tests removed, t27b already passes the other 5 tests (9 asserts), so this is the spec's only blocker.

Acceptance

• The repro passes `t27b test --check`, as a conformance spec under specs/tri/t27b/conformance/.
• queen-public-agents.t27 passes `t27b test --check` with runtime asserts, and its ledger row is `pass`.

User Scenarios

• Given a function with an anytype parameter that is read via @TypeOf and branched on (e.g., if (@TypeOf(value) == i64)), when the function is called with multiple distinct argument types (i64, string, null), then t27b compiles one instance per argument type, folds @TypeOf at compile time, skips false branches, and all assertions pass.

Requirements

• FR-001: t27b MUST monomorphize functions with anytype parameters that are read via @TypeOf, creating one instance per distinct argument type at call sites with deterministic names.
• FR-002: t27b MUST fold @TypeOf(param) == T at compile time per instance.
• FR-003: t27b MUST skip lowering of branches whose condition folds to false, not type-checking them.

Boundary

• specs/port/browseros/trios/agent-server/apps/server/src/api/routes/queen-public-agents.t27
• docs/reports/t27b_expectations.json