Give every API value with a unit as a number (closes #199)

A value with a unit is now a number, and its field name ends in the
unit, as the vendored API_POLICIES.md requires. @meta.execution_time
becomes execution_time_ms. In the stats answers, uptime,
connection_duration, memory_usage and whois_stats.current_interval
become uptime_seconds, connection_duration_seconds, memory_usage_bytes
and whois_stats.current_interval_seconds. connection_duration_seconds
is null while the feed is not connected. The status page formats the
numbers itself. REPO_POLICIES.md is re-vendored from the same
sneak/prompts commit.

Model: opus-5-5

README.md

@@ -113,7 +113,13 @@ one of its peers sends an update.
   figures. The route figures come from the routing table. `oldest_route` and
   `newest_route` are the times of the oldest and the newest kept routes.
   `origins_without_kept_route` counts, across all prefixes, the origin ASes that
-  have no kept route.
+  have no kept route. Other figures include these:
+    - `uptime_seconds`: the number of seconds since the RIS Live feed last
+      connected, or 0 when it has never connected
+    - `memory_usage_bytes`: the size of the Go heap in use, in bytes
+    - `whois_stats.current_interval_seconds`: the WHOIS fetcher's wait between
+      two fetches, in seconds, which can include a fraction of a second
+
 - `GET /.well-known/healthcheck.json` - Health check (JSON): 200 when the
   database answers and the RIS Live feed is connected, otherwise 503;
   `data.status` is `ok` or `error` and `data.checks` says which check failed
@@ -136,9 +142,10 @@ one of its peers sends an update.
 ### API v1
 
 - `GET /api/v1/stats` - The `/status.json` figures plus connection, garbage
-  collector, stream and handler queue statistics. `stream.route_churn_per_min`
-  is the number of prefix announcements and withdrawals, from all peers, in the
-  last full clock minute.
+  collector, stream and handler queue statistics. `connection_duration_seconds`
+  is the number of seconds the RIS Live feed has been connected, or null while
+  it is not connected. `stream.route_churn_per_min` is the number of prefix
+  announcements and withdrawals, from all peers, in the last full clock minute.
 - `GET /api/v1/ip/{ip}` - Looks up each address. `{ip}` is an IP address, a host
   name, or a comma-separated list of at most 10 of these. `results` has one
   entry for each address. Every entry has the same fields:
@@ -207,10 +214,16 @@ one of its peers sends an update.
     missing, empty or only spaces answers 400.
 
 A JSON answer is `{"status": "ok", "data": ...}`, or for an error
-`{"status": "error", "error": {"msg": ..., "code": ...}}`, and carries an
-`@meta` object with the time zone, the API version and the time the request
-took. The health check is the exception: its 503 answer is also
-`{"status": "ok", "data": ...}`, with `error` in `data.status`.
+`{"status": "error", "error": {"msg": ..., "code": ...}}`. The health check is
+the exception: its 503 answer is also `{"status": "ok", "data": ...}`, with
+`error` in `data.status`. Every JSON answer also carries an `@meta` object:
+
+- `time_zone`: always `UTC`
+- `api_version`: `1`
+- `execution_time_ms`: the number of milliseconds the request took
+
+Every value with a unit is a number whose field name ends in the unit, such as
+`_ms`, `_seconds` or `_bytes`.
 
 A request that runs past its time limit answers 504: the limit is 30 seconds,
 and 4 seconds for the database reads behind `/status.json` and `/api/v1/stats`.