Improve BRF inspector diagnostics

[ip332]

Make quarry-brf-inspect failures actionable without changing successful output or runtime APIs.

Improved diagnostics include:

• QBS and BRF file roles, paths, and OS errors;
• explicit BRF stdin read context;
• requested record IDs and names when selection fails;
• semantic malformed QBS and BRF messages;
• output-limit exhaustion versus stdout write failure;
• traversal work, depth, and workspace failures.

Representative messages:

quarry-brf-inspect: unable to read QBS file 'schema.qbs': No such file or directory\nquarry-brf-inspect: record ID 99 not found\nquarry-brf-inspect: malformed BRF input 'record.brf'\nquarry-brf-inspect: output exceeded --max-output-bytes 10\n```\n\nSuccessful inspection output, record discovery, selectors, and stdin behavior are unchanged. Changes are CLI-local to `quarry-brf-inspect` and its focused tests; QBS/BRF formats, runtime APIs, and compatibility epochs are unchanged.