… post-PR #2685 ns normalization

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Co-authored-by: borisbat <272689+borisbat@users.noreply.github.com>

PR GaijinEntertainment#2685 normalized ref_time_ticks() to nanoseconds across every
platform (Windows used to return raw QPC ticks at the underlying
counter's frequency — typically 10 MHz). The fix shipped without a
unit test that would have caught a units regression.

Add four tests under tests/fio/perf_time.das (sleep() lives in fio,
so this is the right neighborhood):

  - monotonic — 1000 successive reads never go backwards. Catches
    any signed/unsigned mixup or wrap-around bug in the ns conversion
    arithmetic.

  - sleep_roundtrip — sleep(100 ms) -> delta_ns must land in
    [80 ms, 500 ms]. The 80 ms lower bound is the load-bearing
    assertion: if Windows reverted to raw QPC ticks (10 MHz counter
    on the typical box -> a 100 ms wall-clock sleep would surface as
    1000000 "ticks" interpreted as ns, i.e. 1 ms), the test would
    trip. Wide upper bound covers CI runner scheduler jitter.

  - get_time_usec_agrees — the get_time_usec(t0) helper agrees with
    (ref_time_ticks() - t0) / 1000 within 5 ms. Two helpers reading
    the same underlying clock should not drift; if one ever ends up
    on a different code path, this notices.

  - units_are_nanoseconds — three back-to-back sleep(100 ms) deltas
    stay within 200 ms spread. If the unit accidentally changed
    mid-run (think: thread-local frequency cache going stale), the
    deltas would diverge wildly.

The test runs cleanly in both interpreter and AOT mode on Windows
(Win11 local): sleep(100 ms) -> 102-109 ms delta, get_time_usec
agrees to within microseconds. tests/aot/CMakeLists.txt:224 already
covers tests/fio/*.das via FILE(GLOB CONFIGURE_DEPENDS); cmake
reconfigure picks the new file up automatically.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

…ssion

Cards added in the course of the linq_fold splice rewrite + PR GaijinEntertainment#2691
(has_sideeffects + counter-lane elision). Topics:

linq_fold / macro-emission patterns:
- daslang-generic-instance-detect-via-fromgeneric — func.fromGeneric is
  the canonical "which generic was this instantiated from?" link;
  func.name on typed instances is mangled.
- daslib-macro-boost-has-sideeffects-predicate — new public predicate,
  full classification table, known limitations, test plumbing.
- qmacro-invoke-source-bind-typedecl-modifier-iter-vs-array — typedecl
  block-param const/ref handling differs between iterator and array
  sources; the two diagnostic error messages tell you which branch you
  picked wrong.
- qmacro-gensym-per-callsite-via-lineinfo — backtick-prefixed names +
  line+column suffix, force_at / force_generated / can_shadow.
- my-fold-macro-emits-a-loop-with-for-it-in-source-... (UPDATED) —
  peel_each pattern corrected for generic-instance detection + positive
  array gate + block-param typedecl handling.

LINQ semantics:
- are-there-parity-tests-in-tests-linq-that-compare-fold-output-to-...
- which-typedecl-predicates-identify-types-where-length-expr-is-...
- why-does-each-arr-fail-with-unsafe-when-not-source-of-for-loop-...
- what-s-the-right-sqlite-linq-chain-form-for-aggregates-sum-min-max-...
- my-macro-substitutes-it-for-a-projection-expression-via-template-...
- when-a-call-macro-needs-to-pick-copy-vs-move-init-for-a-projection-...
- where-does-nolint-rule-go-when-a-lint-warning-is-emitted-from-inside-...

Tooling / ops:
- how-do-i-run-dastest-in-benchmark-only-mode-and-what-s-the-command-...
- cpp-profiler-macos-samply-instruments.md
- what-s-the-end-to-end-checklist-for-adding-a-new-daslib-das-module-...
- how-do-i-call-a-dasimgui-or-any-managed-c-method-on-a-struct-field-...

Updated:
- why-does-my-dastest-integration-test-hang-at-readiness-gate-failed-...
  — original card pointed at a require-order red herring; real cause
  was ref_time_ticks() returning ns on POSIX while wait_until_ready's
  deadline math assumed μs. Fix landed in PR GaijinEntertainment#2685.

No code changes — docs only.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>