Task: Bring ores.platform to the clean standard

ores.platform passes the Component Clean Standard for a component of kind All.

• Every checklist item that applies to a component of kind All passes, with its evidence recorded on the task.
• Every item that does not apply is recorded as not applicable, with the reason.
• Every generator defect found is fixed at its source, with a regression test.
• ores.platform is listed in COMPONENTS_UNDER_TEST, and check_component_drift.py --all passes.

Work the Component Clean Standard in its section order, one entity at a time, and record each item's result in the table below.

1. Baseline and inventory (B01 to B05). Record the baseline before any edit.
2. Models (M01 to M10).
3. Protocol (P01 to P06).
4. Generation (G01 to G06).
5. Wiring and data (W01 to W04).
6. Shell (S01, S02).
7. Structure and hygiene (H01 to H03).
8. Verification (V01 to V06), ending with the registry entry.

Survey, 2026-09-25, at trunk `5de59e3fb8`. Run by an agent that did not write the component, against the clean standard.

• Scale, at baseline. 32 production C++ files in 23 headers and 9 sources, with 7 files under `tests/`. 88 test cases and 201 assertions. 458 C++ files outside the component reference `ores.platform/`, and 383 of them include `ores.platform/time/datetime.hpp`, which makes time the largest surface by a wide margin. The deletions leave 30 production files, 21 headers and 9 sources.
• Suites pass. `ores.platform.tests` runs green from the last build, 201 assertions in 88 test cases.
• What is already clean. No leftover artefact, no commented-out code, no TODO, every file and type name snake_case, folder morphology matches the signed-off catalogue, and the tests target is registered with `add_test` and `add_dependencies(run_all_tests …)`.

Work items, in the order they land.

1. Delete `include/ores.platform/unreachable.hpp`. It has no includer, and `std::unreachable()` is the portable C++23 facility the repo already uses at `ores.nats/src/domain/wire_format.cpp:53`.
2. Delete `include/ores.platform/attributes.hpp`. `ORES_NO_UNIQUE_ADDRESS` is used only by its own three `#define`s, and [[no_unique_address]] is the standard attribute every supported compiler has. Update the audit page, which names the header.
3. Delete `process::get_hostname()`. It duplicates the live `net::get_hostname()` byte for byte and has no caller.
4. Delete `:open_c_file()`. No caller, not even a test.
5. Delete `datetime::is_valid_iso8601_date()`. No caller. It was added for the retired Qt `validateInput()` path.
6. Collapse the duplicated MAC enumerators in `network_info.cpp`. Two hundred and thirty lines to about sixty, one enumerator plus two formatters.
7. Add tests for the three untested source files, `environment.cpp`, `real_environment_provider.cpp` and `executable.cpp`. The environment facet already ships the test seam its own suite never uses.
8. Add tests for untested public API on covered files, starting with `datetime::to_db_string`, which 32 C++ files outside the component call.
9. Remove the vacuous tests and checks. Five `f == f` stability checks, two `has_value()` cases with no else, and three assert-nothing cases.
10. Hygiene. Move the five end-of-line comments above their code, drop the six narration comments, correct the `k_timestamp_format` doc claim, and add the missing `<vector>` include to `file.hpp`.
11. Rewrite `component_overview.org`. Fix the dependency claim, list every facet, drop nothing that exists, fill `See also` with id links, and bump `#+updated`.
12. Fix the generator defect, then refresh the diagram. The automated pass must not delete content, so the generator is fixed at its source with a regression test in the codegen suite, and only then is the diagram refreshed. The `net` and `process` facets hold free functions the automated pass cannot draw, so they are hand-authored below the sentinel.
13. Regenerate the two `component_files.cmake` files, which closes G03 and G06 for this component.

Not this component's work. The other 145 stale `component_files.cmake` files are one repo-wide sweep, and the registry gap needs one programme decision. Both are recorded on the programme story.

All thirteen items landed. Two more defects surfaced while the work was reviewed, and both are fixed here.

• The component-diagram parser had a second defect. A wrapped parameter list leaves a line holding a type, a name and a closing parenthesis, and the member reader took it for a field, so the diagram showed a `format` member that `datetime` does not declare. A candidate field line now needs balanced parentheses of its own, with a regression test.
• `real_environment_provider` had no `ORES_PLATFORM_EXPORT`, and the library builds with `-fvisibility=hidden`, so the class had no external linkage and no test binary could reach it. Every other exported class in the component carries the macro, so this is a latent defect rather than a test convenience.
• Four test files were not clang-format clean. They are now, and `clang-format –dry-run –Werror` is clean on every changed file.

Manual QA scenarios (scaffolded via compass add test_scenario) that verify this task. Link new ones here as they're created; the scenario doc itself links back via its "Verifies task" field.

ores.platform meets the standard for the items that apply to a model-free component. Thirteen work items landed, plus the shared scoped temp types and the diagram corrections, across eight `[platform]` commits.

The component lost five dead public artefacts, seven `file` members with no consumer across four names, and about a hundred lines of duplicated MAC enumeration. It gained tests for three source files that had none, a test for `to_db_string` that 32 C++ files outside the component call, and an assertion count that rose from 201 to 253 with no vacuous case left, and the shared scoped temp file and directory types, which replace seven ad-hoc implementations across the tree once the other components migrate. Two diagram parser defects are fixed at their source with regression tests. The first had made a refresh delete correct content in the seven components that declare a one-line `enum class` in a header, which is what the generator reads.

Two items stay out of scope, both programme-level. The other 145 stale `component_files.cmake` files are one sweep. The registry cannot admit a component with no models, so V06 is the accepted exception and platform does not join `COMPONENTS_UNDER_TEST`.