feat(rapid7-insightidr): feed the layout Process Tree block (v1.9.0)

Rapid7 exposes a process tree per alert; the layout renderer has a block that
draws one. They do not speak the same shape.

The block reads ctx.process_tree as N FLAT chains, root first, each
{alert_id, rule, host, user, nodes[]} — it merges shared ancestors itself.
Rapid7 answers with a NESTED tree: one root entity and children[]. So the
command walks each root-to-leaf path into its own chain, maps the node fields
(cmdline -> cmd_line, hashes.md5 -> md5, start_time -> started_at, pid coerced
from the string Rapid7 sends), and rolls every alert's chains up onto the
investigation, since the block reads the key at the top level and no mapper
expression reaches past alerts[0].

Verified through the block's own reader: a tree of explorer -> cmd ->
{bcdedit, vssadmin} flattens to two chains and comes back as one tree with the
ancestors shared and both leaves marked.

That mark is worth stating plainly. The block marks the last node of a chain as
the target, and Rapid7 flags no node as the one the alert fired on — so here it
means "end of this branch" and nothing stronger. Naming a target would assert
something the sensor never said.

Gated, because this is a third call per alert on top of the evidence one:
include_process_tree=auto (the default) asks only for the event types an
endpoint sensor produces a tree for, true asks for every alert, false never.
An authentication or firewall alert never has one, and on a feed where those
dominate the default saves a call per alert. 404 is treated as "no tree", which
is what it means, and only other statuses are recorded as errors. Bounded at 12
chains and 24 levels so an unexpected shape cannot expand without limit.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

integrations/rapid7-insightidr/mappers/get_investigations_full.yaml

@@ -166,6 +166,13 @@ ocsf:
   # offers, unlike `evidence` above, which only ever shows in the Context tab.
   - { source_path: "alerts[0].evidence_raw_line",          ocsf_field: "raw_data" }
   - { source_path: "alerts[0].evidence_fields.msg ? alerts[0].evidence_fields.msg : alerts[0].evidence_fields.logdesc", ocsf_field: "message" }
+  # ── Process tree ──────────────────────────────────────────────────
+  # The layout block reads ctx.process_tree: N flat chains, root first, each
+  # {alert_id, rule, host, user, nodes[]}. Rapid7 nests its tree through
+  # `children`, so the command flattens each root-to-leaf path into one chain
+  # and rolls every alert's chains up to the investigation — see
+  # get_investigations_full.py. Passed through verbatim; nothing to reshape here.
+  - { source_path: "process_tree", ocsf_field: "process_tree" }
   # ── Every alert, not just the first ───────────────────────────────
   # An investigation aggregates alerts, and the fields above only ever read alerts[0].
   # This entry lands the whole set as OCSF-shaped objects, so the host and the process of