Generate requested line numbers for runtime container log output #304

Problem

Container /log?line_numbers=true responses do not generate line numbers for timestamp-only runtime output. This is a pre-existing V1 limitation also present in the V2 runtime-capture implementation under development in #295; it is being tracked separately to avoid expanding that PR.

Code context

The Docker/Podman capture path requests runtime timestamps and writes the resulting output directly to capture files:

CaptureContainerLogs(..., containers.StreamContainerLogsOptions{
    Follow: true,
    Timestamps: true,
})

The response reader uses:

usvc_io.NewTimestampAwareReader(source, usvc_io.TimestampAwareReaderOptions{
    Timestamps: opts.Timestamps,
    LineNumbers: opts.LineNumbers,
    // ...
})

TimestampAwareReader preserves or removes existing prefixes; it does not generate missing numbering. Relevant code: internal/logs/containerlogs/container_logstreamer.go, internal/docker/cli_orchestrator.go, internal/podman/cli_orchestrator.go, and pkg/io/timestamp_aware_reader.go. V2's analogous implementation is internal/logs/v2containerlogs/container_logstreamer.go in #295.

Reproduction and evidence

A focused streamer probe supplied actual runtime-style input:

2026-10-16T12:00:00.000Z raw-runtime-output

With line_numbers=true and timestamps disabled, the response was raw-runtime-output, rather than 1 raw-runtime-output. This is a controlled reproduction, not a reported production incident. Simulated capture that already includes numbering can mask the defect.

Expected behavior

Honor requested line numbers for runtime stdout/stderr while preserving runtime timestamps and original line positions across tail/skip/limit selections. Keep physical and logical endpoints consistent when consuming the same capture. Existing numbered startup captures must not acquire duplicate prefixes.

Scope and validation

Investigate the existing shared capture/formatting mechanisms before selecting a fix; do not introduce a separate per-source implementation. Cover timestamp-only runtime input, numbering with and without timestamps, and original numbering after tail/skip. This issue does not request changes to runtime lifecycle or watcher dispatch.