.env files written by the CLI do not read back the same values (values with #, surrounding spaces, or newlines) #11314

What happens

The CLI writes .env files in two places and later reads them back with the same parser (parse() in src/functions/env.ts). Some values do not survive the round trip.

1. Function params. When firebase deploy prompts for a param value, it is saved to .env.<projectId> by writeUserEnvs(). A value containing # (for example https://example.com/#/home) or with leading or trailing spaces is written unquoted. The parser treats # as the start of a comment and trims unquoted values, so the next deploy silently uses https://example.com/ or foo instead of what was entered.

2. Extensions. ext:install, ext:configure, ext:update and ext:export write extensions/<instance>.env (and extensions/<instance>.secret.local) as plain KEY=value lines with no quoting or escaping at all. A param value with # is truncated the same way. A value with a newline (for example a multi-line prompt exported from an existing instance) is split across lines; the second line is not a valid entry, readEnvFile() throws, and readInstanceParam() swallows that error, so the whole file is ignored on the next deploy.

What should happen

Any string the CLI writes to a .env file should be read back unchanged.

Minimal repro

// functions
env.writeUserEnvs({ HASH: "https://example.com/#/home" }, opts);
env.loadUserEnvs(opts).HASH; // "https://example.com/", expected "https://example.com/#/home"

// extensions: writeToManifest with params { a: "line one\nline two", b: "#ff0000" }
// writes "a=line one\nline two\nb=#ff0000", which parses to
// { envs: { a: "line one", b: "" }, errors: ["line two"] }

Root cause

formatUserEnvForWrite() only quotes a value when it contains a character that needs an escape sequence (newline, tab, quote, backslash). It does not quote values containing # or starting or ending with whitespace, even though parse() cuts unquoted values at # and trims them. src/extensions/manifest.ts does not use this formatter at all and joins ${key}=${value} directly.