fix(history): count compressed rollouts, read each file once, degrade an unreadable parent

Codex's local_thread_store_compression rewrites cold rollouts to
*.jsonl.zst, which the store scan skipped without a trace. Each one is now
counted in compressedFiles (complete: false), skipped only when its plain
.jsonl sibling exists, as Codex's own discovery does, and a lookup that
misses names the compressed file whose name carries the wanted id. A
Zstandard file given to --file, or sitting in the store under a .jsonl
name, is recognised by its magic number.

Each selected rollout is parsed once into every view later needed of it,
so a legacy copy's boundary proof reuses the parent's own read instead of
charging it to --scan-bytes a second time (and counting its malformed or
inherited records twice).

A parent read that fails for any reason other than a budget now leaves
the boundary unproven (cut at the last candidate, unverifiedPrefixes,
complete: false) instead of failing a child whose own file is intact. A
budget error still fails the read.

--max-bytes is validated before the first file is read, next to the
other budgets, and every budget flag accepts plain decimal integers only.

docs/wiki/Driving-Codeman-From-An-Agent.md

@@ -87,7 +87,8 @@ codeman history read --file /path/to/rollout.jsonl --format text
 - **Forks and sub-agents**: a child's copy of its parent's history is dropped, so every
   record belongs to the thread that wrote it.
 - **`complete: false`** in the JSON means the evidence is partial: a store file that could
-  not be attributed, a record a running Codex is still writing, an ancestor not found.
+  not be attributed, a compressed `.jsonl.zst` rollout (not read), a record a running
+  Codex is still writing, an ancestor not found.
 - **Budgets** fail closed and are raisable: `--metadata-bytes` (attributing the store,
   default 1 GiB), `--max-entries` (65536), `--scan-bytes` (the selected transcripts,
   16 MiB) and `--max-bytes` (output, 8192). `--json` and `--format text` together are an