core-refactor: single-reporter telemetry rewrite (#15933)

Overhaul the telemetry system to enforce a single-reporter model where only the HOST sends terminal statuses (success/failed/aborted) to the API. Containers now write local artifact files (.failed flag + .errinfo) that the host picks up after lxc-attach returns, preventing the race condition where a metadata-less container payload would win over the full host payload.

Key changes:
- Add TELEMETRY_CONTEXT=container export in install.func/alpine-install.func to mark container context before error handling starts
- Introduce _is_container_context() heuristic and _container_write_failure() artifact writer in error_handler.func
- Refactor api.func: unified _tm_payload() builder (full metadata on every send), _tm_send() curl wrapper, _tm_enabled() gate, telemetry_collect_sysinfo() cached collector
- Add structured .errinfo capture in silent() (core.func) using byte-offset to extract exactly the failing command's output
- Pull .errinfo from container in build.func after lxc-attach for precise error traces
- Add categorize_error(), telemetry_new_attempt(), detect_arm(), REPO_SLUG tracking
- Signal exits (129/130/143) now report as 'aborted' instead of 'failed'
- Remove post_update_to_api_extended() (superseded by unified _tm_payload)
- Export REPO_SOURCE, REPO_SLUG, TELEMETRY_PLATFORM into container environment

misc/core.func

@@ -546,6 +546,12 @@ silent() {
   set +Eeuo pipefail
   trap - ERR
 
+  # Byte offset BEFORE the command runs - everything the log grows by is
+  # exactly this command's output (used for the .errinfo telemetry capture)
+  local start_bytes=0
+  [[ -f "$logfile" ]] && start_bytes=$(stat -c%s "$logfile" 2>/dev/null || echo 0)
+  [[ ! "$start_bytes" =~ ^[0-9]+$ ]] && start_bytes=0
+
   "$@" >>"$logfile" 2>&1
   local rc=$?
 
@@ -567,12 +573,43 @@ silent() {
     export _SILENT_FAILED_LINE="$caller_line"
     export _SILENT_FAILED_LOG="$logfile"
 
+    # ── Structured error capture (.errinfo) for telemetry ──
+    # Extract exactly THIS command's output (from the recorded byte offset),
+    # strip ANSI/progress noise, keep the last 60 lines. The host builds the
+    # telemetry error trace from this file (pulled from the container on
+    # failure). Self-contained - containers don't source api.func.
+    {
+      local flat_cmd
+      flat_cmd=$(printf '%s' "$cmd" | tr '\n' ' ' | head -c 300)
+      echo "EXIT_CODE=${rc}"
+      echo "LINE=${caller_line}"
+      echo "COMMAND=${flat_cmd}"
+      echo "--- OUTPUT ---"
+      if [[ -s "$logfile" ]]; then
+        local segment
+        segment=$(tail -c +"$((start_bytes + 1))" "$logfile" 2>/dev/null |
+          sed 's/\r$//' |
+          sed 's/\x1b\[[0-9;]*[a-zA-Z]//g' |
+          grep -avE '^(Get:|Hit:|Ign:|Fetched |Reading package lists|Reading state information|Building dependency tree|Selecting previously|Preparing to unpack|Unpacking |Processing triggers for|\(Reading database|[0-9]+%[[:space:]]*\[)' |
+          grep -avE '^[[:space:]]*$' |
+          tail -n 60)
+        # If the noise filter swallowed everything, fall back to the raw tail
+        if [[ -z "$segment" ]]; then
+          segment=$(tail -c +"$((start_bytes + 1))" "$logfile" 2>/dev/null |
+            sed 's/\r$//' | sed 's/\x1b\[[0-9;]*[a-zA-Z]//g' | tail -n 60)
+        fi
+        printf '%s' "$segment" | head -c 10240
+      fi
+    } >"${logfile}.errinfo" 2>/dev/null || true
+
     return "$rc"
   fi
 
   # Clear stale flags on success (prevents false positives if a previous
   # $STD cmd || true failed and a later non-silent command triggers error_handler)
   unset _SILENT_FAILED_RC _SILENT_FAILED_CMD _SILENT_FAILED_LINE _SILENT_FAILED_LOG 2>/dev/null || true
+  # Also drop a stale .errinfo from a previously tolerated failure ($STD cmd || true)
+  rm -f "${logfile}.errinfo" 2>/dev/null || true
 }
 
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