moq-lite-05: revert Hop ID to varint; reserve 0 as Unknown

[kixelated]

Reverts the Hop ID wire encoding back to a variable-length integer and reserves 0 as a sentinel.

Changes

• Hop ID (ANNOUNCE_OK, ANNOUNCE_BROADCAST) and Exclude Hop (ANNOUNCE_REQUEST): fixed-width (64) → varint (i), dropping the fixed-width rationale text.
• Reserve 0 as "unknown": an assigned Hop ID MUST be non-zero. 0 now unambiguously marks a hop that was either never assigned (e.g. bridging from an older protocol version) or one a relay deliberately withholds to obscure the underlying routing.

Since Hop IDs are random, reserving 0 removes the (vanishing but real) chance an assigned ID collides with the unknown sentinel.

🤖 Generated with Claude Code

[coderabbitai]

Caution

Review failed

Pull request was closed or merged during review

Walkthrough

The draft updates ANNOUNCE_REQUEST, ANNOUNCE_OK, and ANNOUNCE_BROADCAST hop identifier fields from fixed-width 64-bit encoding to variable-length integer encoding. It also changes the described meaning of Hop ID 0 to a reserved unknown/withheld value in ANNOUNCE_OK and ANNOUNCE_BROADCAST, while keeping Hop Count inclusive of unknown hops. The changelog entry describing fixed-width hop ID encoding is removed.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately captures the main wire-encoding change and the new reserved 0 sentinel.
Description check	✅ Passed	The description matches the PR scope, describing the varint encoding changes and the reserved 0 unknown value.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

✨ Simplify code

• Create PR with simplified code
• Commit simplified code in branch claude/silly-dewdney-dc98e1

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