fix(mountsync): prune nested runtime trees before traversal

[khaliqgant]

Problem

Cold Relayfile mounts still paid for one depth=200 ListTree enumeration before the client filtered nested mount runtime artifacts. Production Slack message trees can contain hundreds of .relay/outbox/acked/mountcmd_* leaves, so the traversal hit the runtime cap even though those files were never user content.

Change

• Add one structured full-tree traversal summary with list calls, entries/files/directories/bytes seen, runtime entries, pruned roots, completion/failure, and duration.
• Replace the single depth=200 request with a resumable depth-3 frontier. A nested .relay root is visible and pruned before descendant mountcmd_* leaves can be enumerated.
• Canonicalize and remove only reserved .relay and exact mount state artifacts. Preserve real similarly named content such as .relay-notes, outbox/acked/mountcmd_real.json, and mount state backup files.
• Protect the active mount root runtime directory while removing stale nested runtime trees and tracked state.
• Persist directory plus cursor resume state. Resumed traversals skip authoritative deletion, and legacy deep-list cursors restart safely at root.

Measured regression

The RED fixture against the old depth=200 path returned 414 entries before filtering.

The representative bounded fixture contains 200 Slack message directories and 400 nested runtime mountcmd artifacts. It now completes in exactly 3 ListTree calls, returns zero runtime mountcmd leaves, prunes 200 canonical .relay roots, and remains under the simulated request-latency budget. Real similarly named content is still mirrored.

Validation

• Focused runtime predicate, active-root protection, prune, resume, bootstrap-cursor, and delete-safety regressions pass uncached.
• go test -p 1 ./... passes at head; internal/mountsync completed in 112.804s.
• git diff --check passes and the worktree is clean.

Release and Cloud adoption

This PR must publish a new relayfile-mount release tag after merge. Cloud adoption is a separate PR that bumps RELAYFILE_MOUNT_VERSION in rebuild-snapshot.yml to that released tag and rebuilds the Daytona snapshot. No SDK package bump is involved.

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Review details

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 743df356-2890-423a-bf31-b018dab675fb

📥 Commits

Reviewing files that changed from the base of the PR and between 79685bd and 9d482e3.

📒 Files selected for processing (3)

• internal/mountsync/http_client_test.go
• internal/mountsync/syncer.go
• internal/mountsync/syncer_test.go

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/mount-runtime-tree-prune

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[github-actions]

Relayfile Eval Review

Run: .relayfile/evals/runs/2026-07-18T00-36-52-630Z-HEAD-provider
Mode: provider
Git SHA: 6f8775b

Passed: 4 | Needs human: 0 | Reviewable: 0 | Missing output: 0 | Failed: 0 | Skipped: 0

Human Review Cases

No reviewable human-review cases captured Relayfile output.

[khaliqgant]

Composition update: head moved to 9d482e31649da6cf0f078fdb39d9c3fa7afe9fed. Relayfile Cloud #128 adds the explicit GET/POST excludeMountRuntime capability and enforces the exact mount-runtime predicate in SQL before cursor/order/limit. This Go client now requests that capability on every mount ListTree call, with request-composition coverage. #356 remains HOLD until #128 is SHA-reviewed, merged, and deployed; only then should the client be re-reviewed/merged/tagged and adopted through the Cloud snapshot pin. Full affected go test ./internal/mountsync -count=1 passes in 110.885s.

[khaliqgant]

SHA-bound composition review PASS at 9d482e3. The new client delta opts every mount-originated ListTree request into the server pre-pagination exclusion and proves the exact query shape; exact-head Go/build/E2E/contract/eval/typecheck checks are green. The previously retracted client-only premise is repaired only when paired with relayfile-cloud PR 128. Mandatory gate: PR 128 must merge, deploy, and pass a read-only production opt-in proof before this PR merges or tags. Afterward, pin the new mount binary in Cloud and require a fresh cold fire to reach runner.started.