Generalized error and failure system

More thoughts on error

- Keep a stdout.txt, stderr.txt, and error.log conversion log for each foreign resource, of all stdout/stderr generated... something like `aef/a94a/e4/2b/_logs/stdout.txt`

- Make CLI commands that can show browse log for certain files

--------------------

- Need to have a generalized failure system that permits retries, conversion failures, etc, and escalation after X retries

- For both ConversionGrid and ResolverGrid

- Possibly handle "invalid" stuff too

(from git resolver)
44 # NOTE: Should do validation on GIT resource urls, notably disallowing
45 # HEAD, and branch names (should only be tags or commit hashes)

110 # TODO: Have failure handling here, if this command fails and can't find
111 # given hash, it should attempt to update, if that fails, then we know tha
112 # the specified "tree object" does not exist, 404

Start by locating the ConversionGrid, ResolverGrid, and git resolver implementations, then trace their validation, conversion, and command-failure paths. Define how per-resource stdout.txt, stderr.txt, and error.log records, retries, escalation, invalid resources, and log-browsing CLI commands should work; done requires an agreed generalized failure design covering both grids.

Written by the indexing model from the issue text.