Add node-local snapshot inspection to test infrastructure

[cjen1-msft]

Network.get_committed_snapshots() combines snapshot generation, waiting, and copying into common_dir. Tests that only inspect files or wait for a snapshot do not need those copies: the nodes' directories are already accessible locally.

Add two helpers on Node:

• get_snapshots() returns committed file paths sorted by snapshot seqno. Read-only startup snapshots require include_read_only=True.
• wait_for_snapshot(target_seqno) waits in that node's writable directory for a committed snapshot whose state seqno covers the target.

Neither helper sends requests, generates transactions, or copies files. Returned paths remain node-owned; callers needing durable or mutable copies must copy them explicitly.

Migrate readers in three files:

• e2e_operations.py: election and time-based snapshot waits, plus per-node persistence inventory. Callers sample the commit target explicitly, and counts still deduplicate by filename.
• governance_history.py: read the snapshot covering the target from the existing ledger-chunk setup, rather than the arbitrary last entry from os.listdir(). This removes the old helper's additional ack transactions and relies on normal signature progress to commit the snapshot.
• recovery_snapshot_endorsements.py: compare snapshot bytes in place, including read-only inputs. If a filename exists in both directories, check both copies rather than merging them.

First part of the replacement for #7783. Explicit generation, recovery, joins, and corruption/LTS migrations follow separately; the old helper remains for those callers.

scripts/ci-checks.sh passes. The targeted timing and persistence runs were blocked at startup by the missing logging executable. The migrated end-to-end scenarios still need execution, particularly the governance reader's passive snapshot wait.

[Copilot]

🔵 Needs a closer look

The migrated end-to-end scenarios remain unexecuted, including the passive governance snapshot wait.

Pull request overview

Adds node-local snapshot inspection and waiting helpers, migrating tests away from unnecessary copying and transaction generation.

Changes:

• Adds sorted snapshot listing and passive waiting to Node.
• Updates governance, recovery, timing, and persistence tests.
• Preserves checks across writable and read-only snapshot directories.

File summaries

File	Description
tests/recovery_snapshot_endorsements.py	Verifies snapshot bytes in writable and read-only directories.
tests/infra/node.py	Adds node-local snapshot listing and waiting helpers.
tests/governance_history.py	Selects the snapshot covering the target sequence number.
tests/e2e_operations.py	Migrates snapshot timing, election, and persistence checks.

Review details

• Files reviewed: 4/4 changed files
• Comments generated: 0
• Review effort level: Balanced

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[Amaury Chamayou (achamayou)]

No actionable issues found.

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