chore: bring the lambda scope to 0.3.0

[agustincelentano]

Moves the Lambda scope to 0.3.0, which carries the metrics fix
(nullplatform/scopes-lambda#33).

What it picks up

The performance screen for Lambda scopes was showing container metrics — CPU,
memory, throughput — that a Lambda cannot answer. The cause was assume_role
writing its progress to stdout, which the telemetry workflows hand to the platform
as the response body: the catalog arrived behind two lines of text and could not be
parsed, so GET /metric returned 400 and the UI fell back to the container set.

It also fixes the statistics. Every metric fell back to Sum because the variable
carrying it was never set, so Duration reported 1076 ms where the latency was
2 ms, and ConcurrentExecutions reported 205 where the peak was 1.

And it adds stream.iterator_age, which is what tells whether the consumer of a
DynamoDB stream is falling behind.

Both references move together

Reference	To
agent_repos_extra	0.3.0
scope catalog (nullplatform/locals.tf)	0.3.0

They have to stay in sync: the catalog provides the specs and the agent runs the
scripts, and a mismatch means the platform describes one version while the agent
executes another.

There is no release for this version yet, so 0.3.0 is a branch cut from main
rather than from a tag.

Verified

Applied against the implementation. The agent's pod now clones heads/0.3.0, and
the metric catalog reaches the platform intact — the workflow's stdout starts with
{ instead of the assume_role line, and parses with its six metrics. The
performance screen shows the Lambda graphs and no longer shows the container set.

Note on an unrelated failure

tofu plan in nullplatform/ fails on
module.scope_definitions["containers"].data.external.action_specs["kill-instances"]
with a jq parse error. It reproduces on main without these changes and belongs to
the containers scope, which tracks scopes.git#beta — not to this bump. Worth
looking at separately.

🤖 Generated with Claude Code

[agustincelentano]

Cerrado: quedó obsoleto. Este PR movía el catálogo de 0.2.0 a 0.3.0, y main ya está en 0.4.0 (cf8b5d7), que incluye el mismo fix de métricas más el available_actions del refactor. Mergearlo ahora bajaría la versión.