docs: fix typos in CLI help text and documentation

[Avicennasis]

Summary

Fixes 6 small typos in CLI help text and command documentation. No functional changes - only cobra help/usage strings and doc prose are touched.

• cmd/namespace.go: Namespaces API paths by prefixing it -> ...by prefixing them (the subject "API paths" is plural) - in both the Short and Long descriptions.
• cmd/namespace.go: Eg. 2 API definitions -> E.g. 2 API definitions - every other e.g. in the repo (openapitools/, deckformat/, docs/) is written with both periods.
• cmd/namespace.go: the path based namespace to apply -> the path-based namespace to apply - matches path-based already used at cmd/namespace.go:100 in the same file.
• cmd/patch.go: When using '--selector' and '--values' -> '--value' - the registered flag is --value (singular), as the preceding paragraph in the same help text already says.
• cmd/openapi2mcp.go: generation of entity id's -> generation of entity IDs - plural, not possessive.

No identifiers renamed, no test assertions affected (none of these strings are asserted in tests). Deliberately left alone: the repo's own JSONpath / JSONpointer / JSONobject spellings, which are consistent project-wide and are a maintainer style choice.

[CLAassistant]

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