google_adk.tool_inventories duplicates catalog entries and does not close the incomplete_surface gap it is prescribed for #386

Impact

The remediation the tool prescribes for incomplete_surface does not close the gap, and
makes the headline coverage metric worse. A user who follows the instruction exactly is
left further from a pass than before they started.

This is on the critical path of every ADK adoption: incomplete_surface fires for all six
statically-extracted tools on first scan, and tool_inventories is the only remedy offered.

Severity: P1

Not a cosmetic issue — the loop is unclosable. The instruction is emitted by the tool, the
user complies, and the same verdict comes back with a degraded number. There is no third
step offered.

Reproduction

CLI 0.16.0b7, contract 24. Subject: google/adk-samples#1745,
python/agents/smart_closer.

The verdict instructs:

"Review the skeleton written next to report.json, save it in your repo, reference it from
google_adk.tool_inventories in shipgate.yaml, then rerun verification."

Doing exactly that:

cp agents-shipgate-reports/suggested-inventory.json ./tool-inventory.json
cat >> shipgate.yaml <<'YAML'
google_adk:
  tool_inventories:
    - path: tool-inventory.json
YAML
agents-shipgate scan --format json

Observed

The catalog holds 18 entries but only 12 unique names. Every one of the six inventory
tools is double-counted:

list_messages: 2   get_user_identity: 2   get_manager_email: 2
send_email: 2      map_salesforce_account_to_sap_bp: 2
map_salesforce_product_to_sap_material: 2

Removing the tool_inventories block returns the catalog to 12, confirming the inventory is
the cause.

Root cause

google_adk.tool_inventories is list[ArtifactPathConfig], and ArtifactPathConfig has
only two fields:

path: str      (required)
optional: bool (optional)

There is no field binding an inventory to a tool_source. Confirmed by probing
source_id, id, source, tool_source, tool_source_id, for_source, and source_ref
— all rejected with Extra inputs are not permitted.

So an inventory cannot complete the tools of the source that raised the gap; its entries
are appended to the catalog as new tools that happen to share names. Since the gap is keyed
to the original source's tool (get_manager_email [adk_agent]), it is never satisfied.

Expected behavior

An inventory referenced to resolve incomplete_surface for source adk_agent should raise
that source's tools to high confidence, closing the gap, with the catalog remaining at 12.

Acceptance criteria

• After the documented remediation, incomplete_surface for get_manager_email [adk_agent]
  is closed.
• Catalog size does not grow when an inventory names tools already extracted from a source.
• Either a source-binding field exists on inventory entries, or entries are merged by
  (source_id, tool_name).
• Coverage ratio is monotonic: following a prescribed remediation never lowers it.
• Regression test asserting the ratio does not decrease across a prescribed fix.

Notes

The monotonicity property in criterion 4 is worth a general guard. A remediation that
degrades the metric it was issued to improve will erode trust in every other number the
report prints.