Flaky test fix: Reduce unnecessary reads from live ledgers, and log a warning when they do occur

[eddyashton]

Lots of test cases were caling network.get_latest_ledger_public_state() (dangerous to call on a live node, as it involves reading ledger state), when all they really wanted was network.force_ledger_chunk() and wait. This renames some helpers, and where possible makes them all do the (simpler, safer) latter.

Since this touches lots of call-points which are still constructing a Ledger from a live node, we at least LOG.warning that this is dangerous, hopefully pointing at the root cause for future flaky failures.

[Copilot]

Pull request overview

This PR reduces test flakiness by avoiding unnecessary parsing of ledger data from live nodes. It introduces safer helpers to force ledger chunk creation and wait until the corresponding committed chunk exists on disk, and adds warnings when tests still copy/parse ledgers from live nodes.

Changes:

• Add Network.create_and_wait_for_chunk() to force a ledger chunk and wait until a committed chunk covering a target seqno is present.
• Add Node.get_committed_ledger_dirs() / Node.get_committed_ledger() helpers and emit warnings when copying/parsing ledger files from a live node.
• Update multiple tests to use the new chunk/committed-ledger helpers instead of directly reading/parsing live ledger directories.

Custom instructions used:

• .github/copilot-instructions.md
• .github/instructions/reviewing.instructions.md

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tests/recovery.py	Switch snapshot/ledger-offset recovery flow to wait for committed chunks via new helper.
tests/reconfiguration.py	Replace live-ledger parsing with committed-ledger helpers and chunk waiting.
tests/lts_compatibility.py	Simplify “fresh public state” retrieval and avoid direct in-flight chunk parsing.
tests/jwt_test.py	Replace direct ledger construction with primary.get_committed_ledger() and chunk waiting.
tests/infra/node.py	Add committed-ledger discovery/copy helpers and warnings when operating on live nodes.
tests/infra/network.py	Add create_and_wait_for_chunk() and refactor ledger-public-state helpers to use committed ledger copies.
tests/governance_history.py	Update ledger reads to use committed-ledger helpers and chunk waiting.
tests/e2e_operations.py	Update forced-ledger-chunk test to use new helper and committed ledger reads.

[achamayou]

Suggested change

	target_seqno = seqno if seqno is not None else proposal.completed_seqno
	target_seqno = seqno or proposal.completed_seqno